| BibTeX-Key | Author / Editor / Organization | Title | Year | Journal / Proceedings / Book | BibTeX type | Keywords |
|---|---|---|---|---|---|---|
| BaeSon1993 | Baetzold, R.C. & Song, K.S. | Self-trapped excitons in SrFCl studied by ab initio methods | 1993 |
Physical Review B Vol. 48 (20) , pp. 14907-14914 |
article | |
| Abstract: Self-trapped triplet excitons (STE’s) on the Cl- or F- sublattices of SrFCl have been studied using quantum clusters embedded within point ions or self-consistently within shell-model ions. The unrestricted Hartree-Fock method of calculation is used to treat the clusters. Three possible STE’s are studied. When the in-plane [100] Cl2-STE is displaced from an on-center position the total energy decreases and it becomes basically a one-center species with a hole on one Cl- ion and the excited electron on the incipient Cl- vacancy. The Cl-Cl bond length becomes $3.46rm, reflecting the one-center character of this species. The Cl2- out-of-plane STE behaves similarly with displacement in the [111] direction. The F2- STE remains as a molecular species with displacement in the [110] direction. The hole becomes localized on the F- ion nearest the incipient F- vacancy and on which the excited electron becomes localized. There is a large barrier for electron-hole separation for all of these STE’s. The presence of an adjacent halide vacancy allows the electron and hole to separate into a VK center and an F center without going through an intermediate H center, as occurs in alkali halides. | ||||||
BibTeX:
@article{BaeSon1993,
author = {Baetzold, R C and Song, K S},
title = {Self-trapped excitons in SrFCl studied by ab initio methods},
journal = {Physical Review B},
publisher = {American Physical Society},
year = {1993},
volume = {48},
number = {20},
pages = {14907--14914},
note = {ICECAP},
doi = {http://dx.doi.org/10.1103/PhysRevB.48.14907}
}
|
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| BaeSon1991 | Baetzold, R.C. & Song, K.S. | A study of the structure of the self-trapped exciton in alkali halides by ab initio methods | 1991 |
Journal of Physics: Condensed Matter Vol. 3 (15) , pp. 2499-2505 |
article | |
| Abstract: Hartree-Fock calculations have been performed for various possible geometries of the self-trapped exciton (STE) in several alkali halide crystals. The computations treat a four- to twelve-ion cluster embedded within an ionic lattice representation that may or may not respond self-consistently to the charge distribution in the cluster. Both the triplet and open-shell singlet excited states of the exciton are considered. The energy of each state decreases as the molecular component of the exciton moves from the on-centre D2h symmetry to an off-centre C2v symmetry site. This distortion is accompanied by a separation of the electron and hole components of the exciton leading to a nearest neighbour F-H pair. These findings are in general accord with earlier analyses and one-electron calculations presented by K.S. Song and co-workers (1989). | ||||||
BibTeX:
@article{BaeSon1991,
author = {Baetzold, R C and Song, K S},
title = {A study of the structure of the self-trapped exciton in alkali halides by ab initio methods},
journal = {Journal of Physics: Condensed Matter},
year = {1991},
volume = {3},
number = {15},
pages = {2499-2505},
note = {ICECAP},
url = {http://stacks.iop.org/0953-8984/3/2499}
}
|
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| Cat2000 | Catlow, C.R.A. | Perspective on “Conduction in polar crystals. I. Electrolyte conduction in solid salts” Mott NF, Littleton MJ (1938) Trans Faraday Soc 34: 485 | 2000 |
Theoretical Chemistry Accounts: Theory, Computation, and Modeling (Theoretica Chimica Acta) Vol. 103 (3-4) , pp. 205-208 |
article | |
| Abstract: We survey the consequences of the landmark paper in the development of the contemporary theories of defects in solids – a core area of modern solid-state science. We summarise the basic concepts behind the “Mott–Littleton” approach and the developments to which it has led. | ||||||
BibTeX:
@article{Cat2000,
author = {Catlow, C R A},
title = {Perspective on “Conduction in polar crystals. I. Electrolyte conduction in solid salts” Mott NF, Littleton MJ (1938) Trans Faraday Soc 34: 485},
journal = {Theoretical Chemistry Accounts: Theory, Computation, and Modeling (Theoretica Chimica Acta)},
year = {2000},
volume = {103},
number = {3-4},
pages = {205-208},
note = {ICECAP}
}
|
||||||
| FisHarHarSto1991 | Fisher, A.J.; Harding, J.H.; Harker, A.H. & Stoneham, A.M. Grimes, R.W.; Catlow, C.R.A. & Shluger, A.L. (Hrsg.) | Embedded Cluster Calculations of Defect Processes | 1991 |
Reviews of Solid State Science Vol. 5 Quantum Mechanical Cluster Calculations in Solid State Studies , pp. 133-147 |
article | |
BibTeX:
@article{FisHarHarSto1991,
author = {Fisher, A J and Harding, J H and Harker, A H and Stoneham, A M},
title = {Embedded Cluster Calculations of Defect Processes},
booktitle = {Quantum Mechanical Cluster Calculations in Solid State Studies},
journal = {Reviews of Solid State Science},
year = {1991},
volume = {5},
pages = {133-147},
note = {ICECAP}
}
|
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| GriCat1990 | Grimes, R.W. & Catlow, C.R.A. | Modeling Localized Defects in Ionic Materials Using Mott-Littleton and Embedded Quantum Cluster Methodology | 1990 |
Journal of the American Ceramic Society Vol. 73 (11) , pp. 3251-3256 |
article | |
| Abstract: Embedded quantum cluster and Mott-Littleton techniques are used to study defects in MgO, UO2, and FeO. Through these calculations we illustrate the importance of lattice relaxation and provide evidence that the quantum cluster methodology is both compatible with and complementary to a Born-like ionic model. We discuss the limitations of both methods. Within the Mott-Littleton framework we consider the derivation of effective pair potentials, region sizes, and the application to complex systems. For embedded quantum cluster calculations we investigate basis sets and discuss effective embedding procedures. | ||||||
BibTeX:
@article{GriCat1990,
author = {Grimes, R W and Catlow, C R A},
title = {Modeling Localized Defects in Ionic Materials Using Mott-Littleton and Embedded Quantum Cluster Methodology},
journal = {Journal of the American Ceramic Society},
year = {1990},
volume = {73},
number = {11},
pages = {3251-3256},
note = {ICECAP}
}
|
||||||
| GriCatShlPanBaeHar1991 | Grimes, R.W.; Catlow, C.R.A.; Shluger, A.L.; Pandey, R.; Baetzold, R. & Harker, A.H. Bristowe, P.D.; Epperson, J.E. & Griffith, J E snd Lilientalweber, Z. (Hrsg.) | Simulating Vacancy, Impurity and Electronic Defect States in MgO, LiCl and $rm La_2CuO_$4 Using Quantum Cluster and Classical Lattice Simulation Techniques in a Consistent Manner | 1991 |
Vol. 14th International Symposium on Characterization of Defects in Materials, Boston, Ma, November 26-29, 1990 (209) Defects In Materials , pp. 257-262 |
inproceedings | |
BibTeX:
@inproceedings{GriCatShlPanBaeHar1991,
author = {Grimes, R W and Catlow, C R A and Shluger, A L and Pandey, R and Baetzold, R and Harker, A H},
title = {Simulating Vacancy, Impurity and Electronic Defect States in MgO, LiCl and $rm La_2CuO_$4 Using Quantum Cluster and Classical Lattice Simulation Techniques in a Consistent Manner},
booktitle = {Defects In Materials},
year = {1991},
volume = {14th International Symposium on Characterization of Defects in Materials, Boston, Ma, November 26-29, 1990},
number = {209},
pages = {257-262},
note = {ICECAP}
}
|
||||||
| GroPanRec1994 | Groh, D.; Pandey, R. & Recio, J.M. | Embedded Quantum Cluster Study of Local Relaxations and Optical Properties of $rm Cr^3+$ in MgO | 1994 |
Physical Review B Vol. 50 (20) , pp. 14860-14866 |
article | |
| Abstract: Local distortions and optical properties induced by the substitutional Cr3+ impurity in the MgO host lattice are computed using the embedded-cluster approach implemented in the icecap code. Within this methodology, the impurity centered cluster is described quantum mechanically and is self-consistently coupled with the lattice environment by means of the shell-model treatment of the lattice polarization and distortion. Our calculations predict inward relaxations of the six O2- nearest neighbors surrounding the Cr3+ ion for both cubic and noncubic (tetragonal and orthorhombic) configurations in MgO. For the cubic configuration, selected low-lying excited states, including the 10Dq generator 4T2, are calculated at several Cr-O separations. After taking into account lattice relaxations and correlation corrections, the computed 10Dq value lies 0.19 eV lower than the experimental one. Finally, the response of the Dq parameter and the Cr-O separation to hydrostatic pressure is obtained by performing analogous cluster-in-the-lattice calculations with the lattice parameter of MgO varying according to its equation of state. Analysis of these results reveals that the compressibility at the host cation site is greater than that at the impurity site. | ||||||
BibTeX:
@article{GroPanRec1994,
author = {Groh, D and Pandey, R and Recio, J M},
title = {Embedded Quantum Cluster Study of Local Relaxations and Optical Properties of $rm Cr^3+$ in MgO},
journal = {Physical Review B},
year = {1994},
volume = {50},
number = {20},
pages = {14860-14866},
note = {ICECAP}
}
|
||||||
| HarHarKeePanVaiWoo1985 | Harding, J.H.; Harker, A.H.; Keegstra, P.B.; Pandey, R.; Vail, J.M. & Woodward, C. | Hartree-Fock Cluster Computations Of Defect And Perfect Ionic Crystal Properties | 1985 |
Physica B & C Vol. 131 (1-3) , pp. 151-156 |
article | |
BibTeX:
@article{HarHarKeePanVaiWoo1985,
author = {Harding, J H and Harker, A H and Keegstra, P B and Pandey, R and Vail, J M and Woodward, C},
title = {Hartree-Fock Cluster Computations Of Defect And Perfect Ionic Crystal Properties},
journal = {Physica B & C},
year = {1985},
volume = {131},
number = {1-3},
pages = {151-156},
note = {ICECAP}
}
|
||||||
| KunVai1988 | Kunz, A.B. & Vail, J.M. | Quantum-mechanical cluster-lattice interaction in crystal simulation: Hartree-Fock method | 1988 |
Physical Review B Vol. 38 (2) , pp. 1058-1063 |
article | |
| Abstract: The problem of describing quantum mechanically a region of interest in an otherwise extended lattice is discussed for nonmetallic solids. A localizing potential to accomplish this is described, and its implications for the total-energy algorithm are analyzed. A spurious tunneling effect that may arise with a finite embedding lattice is also discussed. | ||||||
BibTeX:
@article{KunVai1988,
author = {Kunz, A Barry and Vail, John M},
title = {Quantum-mechanical cluster-lattice interaction in crystal simulation: Hartree-Fock method},
journal = {Physical Review B},
publisher = {American Physical Society},
year = {1988},
volume = {38},
number = {2},
pages = {1058--1063},
note = {ICECAP},
doi = {http://dx.doi.org/10.1103/PhysRevB.38.1058}
}
|
||||||
| MenJenVai1990 | Meng, J.; Jena, P. & Vail, J.M. | Hole trapping in LixNi1-xO | 1990 |
Journal of Physics: Condensed Matter Vol. 2 (51) , pp. 10371-10377 |
article | |
| Abstract: Calculations are reported for a hole associated with a lithium impurity in NiO. The method is based on Hartree-Fock molecular clusters embedded in a classical shell-model lattice, with consistent treatment of distortion and polarization. It is shown that the hole is trapped in oxygen 2p states rather than in nickel 3d states, in agreement with experimental X-ray absorption spectroscopy results. In the static lattice approximation the hole localizes on a single oxygen nearest neighbour of the lithium ion, rather than in an Oh-symmetric distribution among all such neighbours. | ||||||
BibTeX:
@article{MenJenVai1990,
author = {Meng, J and Jena, P and Vail, J M},
title = {Hole trapping in LixNi1-xO},
journal = {Journal of Physics: Condensed Matter},
year = {1990},
volume = {2},
number = {51},
pages = {10371-10377},
note = {ICECAP},
url = {http://stacks.iop.org/0953-8984/2/10371}
}
|
||||||
| MenKunWoo1988 | Meng, J.; Kunz, A.B. & Woodward, C. | Electronic structure and optical properties of the impurity $Cu+$ in NaF | 1988 |
Phys. Rev. B Vol. 38 (15) , pp. 10870-10873 |
article | |
| Abstract: The electronic structure of the impurity Cu+ in a sodium fluoride crystal has been studied using the ICECAP (ionic crystal with electronic cluster, automatic program) methodology, which treats the defect and its vicinity quantum mechanically as a molecular cluster embedded in a shell-model lattice. The electrons in the cluster have been treated in the unrestricted Hartree-Fock self-consistent-field approximation, corrected for correlation by use of the many-body perturbation theory. The surrounding infinite lattice has been described by the shell model that incorporates host polarization and distortion self-consistently. The basis sets used to describe the Cu+ ion were optimized. The excitation energy and the crystal-field splitting were computed as 4.02 and 0.31 eV, respectively, versus the corresponding experimental results of 4.20 and 0.35 eV, respectively. | ||||||
BibTeX:
@article{MenKunWoo1988,
author = {Meng, Jie and Kunz, A Barry and Woodward, Christopher },
title = {Electronic structure and optical properties of the impurity $Cu+$ in NaF},
journal = {Phys. Rev. B},
publisher = {American Physical Society},
year = {1988},
volume = {38},
number = {15},
pages = {10870--10873},
note = {ICECAP},
doi = {http://dx.doi.org/10.1103/PhysRevB.38.10870}
}
|
||||||
| MenPanVaiKun1989 | Meng, J.; Pandey, R.; Vail, J.M. & Kunz, A.B. | Impurity potentials derived from embedded quantum clusters: $rm Ag^+$ and $rm Cu^+$ transport in alkali halides | 1989 |
Journal of Physics: Condensed Matter Vol. 1 , pp. 6049-6058 |
article | |
| Abstract: Short-range shell-model potentials between substitutional Ag+ ions and host-lattice halide ions in RbCl, KCI, NaC, and NaF are derived using the ICECAP methodology. In this method the impurity and its nearest neighbours are treated as an embedded quantum cluster in unrestricted Hartree-Fock self-consistent field approximation. The embedding lattice is described by the shell model. The consistency of the derivation is tested in various ways. The potentials are then applied to calculate activation energies for diffusion by vacancy and interstitial mechanisms for Ag+. Previously derived potentials for Cu+ are used to calculate interstitial diffusion activation energies in KCI and NaCI. The potentials are tested for transferability from one host crystal to another. Deficiencies of the method are discussed and improvements are identified. |
||||||
BibTeX:
@article{MenPanVaiKun1989,
author = {Meng, Jie and Pandey, Ravindra and Vail, John M and Kunz, A Barry},
title = {Impurity potentials derived from embedded quantum clusters: $rm Ag^+$ and $rm Cu^+$ transport in alkali halides},
journal = {Journal of Physics: Condensed Matter},
year = {1989},
volume = {1},
pages = {6049-6058},
note = {ICECAP}
}
|
||||||
| MenPanVaiKun1988 | Meng, J.; Pandey, R.; Vail, J.M. & Kunz, A.B. | $Cu+$ diffusion and interionic potentials for $Cu+$ in alkali halides | 1988 |
Phys. Rev. B Vol. 38 (14) , pp. 10083-10086 |
article | |
| Abstract: Short-range interionic potentials for the substitutional Cu+ ion in alkali fluorides and chlorides are derived using a methodology that provides self-consistent electronic-structure treatment of a molecular cluster of ions that includes the impurity, embedded in a shell model lattice. The derived potentials are used to calculate the activation energy for Cu+ diffusion by the cation vacancy mechanism in these materials. For the only case where an experimental value is available, namely, KCl:Cu+, satisfactory agreement is found. | ||||||
BibTeX:
@article{MenPanVaiKun1988,
author = {Meng, J. and Pandey, Ravindra and Vail, J. M. and Kunz, A. Barry},
title = {$Cu+$ diffusion and interionic potentials for $Cu+$ in alkali halides},
journal = {Phys. Rev. B},
publisher = {American Physical Society},
year = {1988},
volume = {38},
number = {14},
pages = {10083--10086},
note = {ICECAP},
doi = {http://dx.doi.org/10.1103/PhysRevB.38.10083}
}
|
||||||
| MenVaiStoJen1990 | Meng, J.; Vail, J.M.; Stoneham, A.M. & Jena, P. | Charge-state stability of Ni and Cu impurities in MgO | 1990 |
Phys. Rev. B Vol. 42 (2) , pp. 1156-1162 |
article | |
| Abstract: Total energies for substitutional Ni and Cu ions in MgO are studied for their 1+, 2+, and 3+ charge states. These are used to assess charge-state stability. Specifically, electron loss to the conduction band for Ni+ and electron capture from the valence band for Ni3+ and Cu3+ are considered. The impurity and its near-neighboring ions are analyzed in the unrestricted Hartree-Fock self-consistent-field approximation, as a molecular cluster embedded in a consistently relaxed shell-model lattice. The results indicate that both electron loss for n=1 and electron capture for n=3 should occur, so that disproportionation of the various charge states is intrinsically unstable. | ||||||
BibTeX:
@article{MenVaiStoJen1990,
author = {Meng, J. and Vail, J. M. and Stoneham, A. M. and Jena, P. },
title = {Charge-state stability of Ni and Cu impurities in MgO},
journal = {Phys. Rev. B},
publisher = {American Physical Society},
year = {1990},
volume = {42},
number = {2},
pages = {1156--1162},
note = {ICECAP},
doi = {http://dx.doi.org/10.1103/PhysRevB.42.1156}
}
|
||||||
| PanKun1990 | Pandey, R. & Kunz, A.B. | Characterization of fluorine-doped magnesium oxide: A computer simulation study | 1990 |
Journal of Physics and Chemistry of Solids Vol. 51 (8) , pp. 929 - 931 |
article | magnesium oxide |
| Abstract: A computer simulation study is performed to characterize F--doped MgO. The impurity potentials, namely F--Mg2+ and F--O2- are derived using ICECAP and are then used to study F- diffusion in MgO. The activation energy by vacancy mechanism comes out to be 1.53 eV. The excitonic state associated with the F- ion is also studied. Furthermore, the excess electron associated with the F- ion is predicted to be unbound in the lattice. | ||||||
BibTeX:
@article{PanKun1990,
author = {Pandey, Ravindra and Kunz, A Barry},
title = {Characterization of fluorine-doped magnesium oxide: A computer simulation study},
journal = {Journal of Physics and Chemistry of Solids},
year = {1990},
volume = {51},
number = {8},
pages = {929 - 931},
note = {ICECAP},
url = {http://www.sciencedirect.com/science/article/B6TXR-46MTRPJ-8K/2/48cae8a01274622a1f5a3451615a3833},
doi = {DOI: 10.1016/0022-3697(90)90034-D}
}
|
||||||
| PanKunVai1988 | Pandey, R.; Kunz, A.B. & Vail, J.M. | Study of point defects in alkaline-earth sulfides | 1988 |
Journal of Materials Research Vol. 3 (6) , pp. 1362-1366 |
article | |
| Abstract: The results of a computer simulation study of point defects including vacancy, interstitial, and F+ center in alkaline-earth sulfides are presented. The study is based on ICECAP/HADES simulation procedures and uses empirical interionic potentials obtained from the analysis of macroscopic data for these materials. The results predict the dominance of Schottky disorder and suggest that vacancy migration predominates in alkaline-earth sulfides. Furthermore, the calculated F+ center absorption energy is in good agreement with the experimental data deduced from the optical stimulated studies in these materials. | ||||||
BibTeX:
@article{PanKunVai1988,
author = {Pandey, Ravindra and Kunz, A Barry and Vail, John M},
title = {Study of point defects in alkaline-earth sulfides},
journal = {Journal of Materials Research},
year = {1988},
volume = {3},
number = {6},
pages = {1362-1366},
note = {ICECAP}
}
|
||||||
| PanSiv1991 | Pandey, R. & Sivaraman, S. | Spectroscopic properties of defects in alkaline-earth sulfides | 1991 |
Journal of Physics and Chemistry of Solids Vol. 52 (1) , pp. 211 - 225 |
article | alkaline-earth sulfides |
| Abstract: Spectroscopic properties of pure and impurity-activated alkaline-earth sulfides as studied by optical and magnetic resonance techniques are reviewed. | ||||||
BibTeX:
@article{PanSiv1991,
author = {Pandey, Ravindra and Sivaraman, S},
title = {Spectroscopic properties of defects in alkaline-earth sulfides},
journal = {Journal of Physics and Chemistry of Solids},
year = {1991},
volume = {52},
number = {1},
pages = {211 - 225},
note = {ICECAP},
url = {http://www.sciencedirect.com/science/article/B6TXR-46MMNN9-RM/2/4ee280cc81840da468b36611890d1baf},
doi = {DOI: 10.1016/0022-3697(91)90066-9}
}
|
||||||
| PanVai1989 | Pandey, R. & Vail, J.M. | F-type centres and hydrogen anions in MgO: Hartree-Fock ground states | 1989 |
Journal of Physics: Condensed Matter Vol. 1 (17) , pp. 2801-2820 |
article | |
| Abstract: Second-neighbour defect clusters, described in the Hartree-Fock approximation with Kunz-Klein localising potentials out to fourth neighbours, embedded in an infinite shell model lattice are analysed with consistent distortion and polarisation for F+, F (H-)+, and (H2-)0 defects in MgO. Basis sets for the defects are optimised, and are improved by recontraction for the first and second neighbours. Questions of total energy, nearest-neighbour displacements and localisation are addressed for each defect. For the F+ centre, its ground state in relation to the valence band is discussed, as is the localisation of its unrelaxed excited state. For the F+ and (H2-)0 centres, spin densities are evaluated at each step of the calculation, and compared with experiment. Calculations that completely neglect the ion-size effect of all ions except at the defect centre give some qualitatively plausible results. The full-cluster results are used to derive short-range shell model parameters for H-and H2- in MgO. The method and results are critically reviewed. | ||||||
BibTeX:
@article{PanVai1989,
author = {Pandey, R and Vail, J M},
title = {F-type centres and hydrogen anions in MgO: Hartree-Fock ground states},
journal = {Journal of Physics: Condensed Matter},
year = {1989},
volume = {1},
number = {17},
pages = {2801-2820},
note = {ICECAP},
url = {http://stacks.iop.org/0953-8984/1/2801}
}
|
||||||
| PanZuoKun1990 | Pandey, R.; Zuo, J. & Kunz, A.B. | Derivation of Interionic Potentials Using Embedded Quantum-Mechanical Clusters: Cation and Anion Impurities in MgO. | 1990 |
Journal of Materials Research Vol. 5 (3) , pp. 623-628 |
article | ceramics, refractories and glass, inorganic chemistry, crystallography |
| Abstract: The ICECAP methodology is used to derive interionic potentials of some cation and anion impurities in MgO, namely, Li(+), Na(+), K(+), Be(+2), H(-), S(-2) and O(-2). Analysis is given of the defect energies obtained by using the derived impurity potentials. Based on the available experimental data, comparison is made to justify the reliability of the derived impurity potential for Be(+2). The calculated activation energy for Be(+2) diffusion comes out to be 1.54 eV as compared to the experimental value of 1.60 eV, which is considered to be very satisfactory. | ||||||
BibTeX:
@article{PanZuoKun1990,
author = {Pandey, R and Zuo, J and Kunz, A B},
title = {Derivation of Interionic Potentials Using Embedded Quantum-Mechanical Clusters: Cation and Anion Impurities in MgO.},
journal = {Journal of Materials Research},
year = {1990},
volume = {5},
number = {3},
pages = {623-628},
note = {ICECAP}
}
|
||||||
| PanZuoKun1989 | Pandey, R.; Zuo, J. & Kunz, A.B. | Excitonic states in pure and impurity-doped magnesium oxide | 1989 |
Phys. Rev. B Vol. 39 (17) , pp. 12565-12567 |
article | |
| Abstract: Excitonic states in pure and anion-impurity-doped MgO are investigated in several well-defined models using unrestricted Hartree-Fock (UHF)/icecap (ionic crystal with electronic cluster, automatic program) simulation procedures. The calculated excitation energies in pure MgO are in excellent agreement with the experiment. The results for S2-- or Se2--doped MgO show quite conclusively that the lattice response needs to be consistently incorporated with the defect electronic structure. | ||||||
BibTeX:
@article{PanZuoKun1989,
author = {Pandey, Ravindra and Zuo, Jun and Kunz, A. Barry},
title = {Excitonic states in pure and impurity-doped magnesium oxide},
journal = {Phys. Rev. B},
publisher = {American Physical Society},
year = {1989},
volume = {39},
number = {17},
pages = {12565--12567},
note = {ICECAP},
doi = {http://dx.doi.org/10.1103/PhysRevB.39.12565}
}
|
||||||
| PunVelPan1994 | Puntambekar, U.; Veliah, S. & Pandey, R. | Point-defects in magnesium sulfide | 1994 |
Journal of Materials Research Vol. 9 (1) , pp. 132-134 |
article | |
| Abstract: The results of a study of point defects in MgS are presented. First we obtain empirical interionic potentials in the framework of a shell model and then calculate defect energies using the HADES and ICECAP simulation procedures. The calculated Schottky formation energy is 10.9 eV in comparison to the cation and anion Frenkel formation energies of 11.9 and 25.1 eV, respectively. The migration energy by the vacancy mechanism of the Mg2+ and S2- ions is predicted to be 2.5 and 3.4 eV, respectively. One-electron ICECAP calculations yield the optical absorption energy of 3.1 eV for the F+ center in MgS. | ||||||
BibTeX:
@article{PunVelPan1994,
author = {Puntambekar, Upendra and Veliah, Sunder and Pandey, Ravindra},
title = {Point-defects in magnesium sulfide},
journal = {Journal of Materials Research},
year = {1994},
volume = {9},
number = {1},
pages = {132-134},
note = {ICECAP}
}
|
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| ShlGriCat1991 | Shluger, A.L.; Grimes, R.W. & Catlow, C.R.A. | A new model for the self-trapped exciton in alkali halides | 1991 |
Journal of Physics: Condensed Matter Vol. 3 (18) , pp. 3125-3128 |
article | |
| Abstract: The authors report a quantum mechanical study of the structural and spectroscopic properties of the self-trapped exciton in LiCl. Their method interfaces the quantum cluster calculations on a Li10Cl4 cluster with a Mott-Littleton treatment of the relaxation of the surrounding lattice. Calculations on the Vk centre give structures that are in very good agreement with Mott-Littleton calculations, and yield optical absorption energies that compare well with experimental values. Their study of the triplet ground state of the self-trapped exciton reveals a minimum energy structure of C2v symmetry caused by a small of f-centre displacement (of approximately=0.07 AA) of the Cl2- (Vk) ions which comprise the hole component of the exciton. The electron is in a largely delocalized state around the hole with both components localized more on the Cl ion that is displaced towards the perfect lattice site. The magnitude of the off-centre displacement is much less than in the earlier studies of Song et al. (1990). A key feature in the success of these calculations was the self-consistent polarization of the surrounding lattice to the quantum cluster. | ||||||
BibTeX:
@article{ShlGriCat1991,
author = {Shluger, A L and Grimes, R W and Catlow, C R A},
title = {A new model for the self-trapped exciton in alkali halides},
journal = {Journal of Physics: Condensed Matter},
year = {1991},
volume = {3},
number = {18},
pages = {3125-3128},
note = {ICECAP},
url = {http://stacks.iop.org/0953-8984/3/3125}
}
|
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| ISI:A1992JY84400005 | Shluger, A.L.; Harker, A.H.; Grimes, R.W. & Catlow, C.R.A. | Crystal Excitation - Survey of Many-Electron Hartree-Fock Calculations of Self-Trapped Excitons In Insulating Crystals | 1992 |
Philosophical Transactions of the Royal Society A-Mathematical Physical and Engineering Sciences Vol. 341 (1661) , pp. 221-231 |
article | |
| Abstract: To model successfully the diversity of electronic structure exhibited by excitons in alkali halides and in oxide materials, it is necessary to use a variety or combination of theoretical methods. In this review we restrict our discussion to the results of embedded quantum cluster calculations. By considering the results of such studies, it is possible to recognize the general similarities and differences in detail between the various exciton models in these materials. | ||||||
BibTeX:
@article{ISI:A1992JY84400005,
author = {Shluger, A L and Harker, A H and Grimes, R W and Catlow, C R A},
title = {Crystal Excitation - Survey of Many-Electron Hartree-Fock Calculations of Self-Trapped Excitons In Insulating Crystals},
journal = {Philosophical Transactions of the Royal Society A-Mathematical Physical and Engineering Sciences},
year = {1992},
volume = {341},
number = {1661},
pages = {221-231},
note = {ICECAP}
}
|
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| ISI:A1993MP24800009 | Shluger, A.L.; Harker, A.H.; Puchin, V.E.; Itoh, N. & Catlow, C.R.A. | Simulation of Defect Processes - Experiences With the Self-Trapped Exciton | 1993 |
Modelling and Simulation in Materials Science and Engineering Vol. 1 (5) , pp. 673-692 |
article | |
| Abstract: We present a critical analysis of the applicability of cluster ab initio many-electron methods to studies of the structure and spectroscopic properties of defects in insulating crystals on the basis of comparison of the results of recent calculations with experimental data for self-trapped excitons. These are archetypal intrinsic defects and the calculation of their properties illustrates almost all the characteristic features of defect studies, including the study of the atomic and electronic structure, diffusion and spectroscopic parameters. | ||||||
BibTeX:
@article{ISI:A1993MP24800009,
author = {Shluger, A L and Harker, A H and Puchin, V E and Itoh, N and Catlow, C R A},
title = {Simulation of Defect Processes - Experiences With the Self-Trapped Exciton},
journal = {Modelling and Simulation in Materials Science and Engineering},
year = {1993},
volume = {1},
number = {5},
pages = {673-692},
note = {ICECAP}
}
|
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| ShlItoPucHei1991 | Shluger, A.L.; Itoh, N.; Puchin, V.E. & Heifets, E.N. | Two types of self-trapped excitons in alkali halide crystals | 1991 |
Phys. Rev. B Vol. 44 (4) , pp. 1499-1508 |
article | |
| Abstract: We have carried out ab initio many-electron variational calculations of the adiabatic potential-energy surface (APES) for the lowest triplet state of the self-trapped exciton (STE) in KCl and LiCl. For KCl, it is found that at the APES minimum, the Cl2- molecular ion comprising the STE hole is displaced along the 110 axis by about $0.90rm from its symmetrical position. The STE electron and hole are shifted in the direction opposite to that of the Cl2- displacement. The calculated optical-transition energies due to electron and hole excitations of the STE at the APES minimum, and the luminescence energy due to the transition to the crystal ground state agree well with the experimental results. It is found that the 110 displacement of the Cl2- molecular ion at the APES minimum from its symmetrical position for LiCl is $0.07rm, much smaller than that in KCl, and that the direction of the shift of the electron and hole is opposite to that for KCl; the electron and hole are localized near one of the Cl2- ions located closer to the lattice site. It is shown that, for a small shift of the Cl2- molecular ion from its symmetrical position, the states in which electron and hole are shifted to opposite directions appear in both LiCl and KCl crystals within energy intervals less than 0.8 eV. It is pointed out that the configuration interaction between the two states with the electron and hole shifted in opposite directions should be included for more precise APES calculations at small off-center displacements, and that the electron-hole correlation is important to determine the electronic structure of the STE. | ||||||
BibTeX:
@article{ShlItoPucHei1991,
author = {Shluger, A L and Itoh, N and Puchin, V E and Heifets, E N},
title = {Two types of self-trapped excitons in alkali halide crystals},
journal = {Phys. Rev. B},
publisher = {American Physical Society},
year = {1991},
volume = {44},
number = {4},
pages = {1499-1508},
note = {ICECAP},
doi = {http://dx.doi.org/10.1103/PhysRevB.44.1499}
}
|
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| SonBae1992 | Song, K.S. & Baetzold, R.C. | Structure of the self-trapped exciton and nascent Frenkel pair in alkali halides: An ab initio study | 1992 |
Phys. Rev. B Vol. 46 (4) , pp. 1960-1969 |
article | |
| Abstract: Adiabatic-potential-energy surfaces of the self-trapped exciton (STE) of both the spin-singlet and -triplet states in NaF, NaCl, and NaBr are calculated with use of ab initio Hartree-Fock cluster methods. In all cases, there is clear evidence of adiabatic instability in the on-center geometry. The STE undergoes a spontaneous symmetry-breaking relaxation, resulting in a structure which is equivalent to an F-H center pair (a Frenkel defect pair in the anion sublattice). The potential energy is remarkably flat, to within about 0.2 eV, for further separation of the H center from the F center up to a distance of about $3rm, the largest distance attained in this study. In view of the flat nature of the excited-state energy surface, and given the difficulties inherent in an ab initio computation, the calculated recombination energies are found to be within an acceptable range of values when compared with experiment for both the $ and $ bands. From this work, the initial state of the $ emission band is attributed to the singlet STE of the lowest orbital state. On the basis of the adiabatic potential energies obtained in this work, a mechanism of $-band quenching is proposed. | ||||||
BibTeX:
@article{SonBae1992,
author = {Song, K. S. and Baetzold, R. C.},
title = {Structure of the self-trapped exciton and nascent Frenkel pair in alkali halides: An ab initio study},
journal = {Phys. Rev. B},
publisher = {American Physical Society},
year = {1992},
volume = {46},
number = {4},
pages = {1960--1969},
note = {ICECAP},
doi = {http://dx.doi.org/10.1103/PhysRevB.46.1960}
}
|
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| Sto1987 | Stoneham, A.M. | Quantitative modelling of defect processes in ionic crystals | 1987 |
Physics and Chemistry of Minerals Vol. 14 (5) , pp. 401-406 |
article | |
| Abstract: This paper is concerned with the accurate prediction of defect properties and processes by quantum methods, with emphasis on ionic systems. Such approaches are of especial value for situations where direct experiment is difficult because of timescale or of extremes of temperature or pressure. In most cases one has to solve an electronic structure problem coupled with a technique for including polarisation and distortion of the surrounding solid. Such polarisation terms can be large and even dominant, and usual simplistic approaches are insufficient. I discuss several aspects, all including use of empirical potentials, namely (i) strategies for combining electronic structure and distortion, (ii) classical calculations of quantum energies, and (iii) cases where one needs quantum dynamics. Examples are given for work expoiting codes developed at Harwell. | ||||||
BibTeX:
@article{Sto1987,
author = {Stoneham, A M},
title = {Quantitative modelling of defect processes in ionic crystals},
journal = {Physics and Chemistry of Minerals},
year = {1987},
volume = {14},
number = {5},
pages = {401-406},
note = {ICECAP}
}
|
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| Vai1996 | Vail, J.M. Kaplan, T.A. & Mahanti, S.D. (Hrsg.) | Embedding Theory and Quantum Cluster Simulation of Point Defects in Ionic Crystals | 1996 | Electronic Properties of Solids Using Cluster Methods , pp. 29-39 | incollection | |
BibTeX:
@incollection{Vai1996,
author = {Vail, J M},
title = {Embedding Theory and Quantum Cluster Simulation of Point Defects in Ionic Crystals},
booktitle = {Electronic Properties of Solids Using Cluster Methods},
publisher = {Springer US},
year = {1996},
pages = {29-39},
note = {ICECAP}
}
|
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| Vai1990 | Vail, J.M. | Theory of electronic defects: Applications to MgO and alkali halides | 1990 |
Journal of Physics and Chemistry of Solids Vol. 51 (7) , pp. 589 - 607 |
article | ionic crystals |
| Abstract: The topic of electronic defects is introduced with the example of a defect electronic transition, and its role in the F-center lasers. Predictive and methodological objectives of a theory of electronic defects are briefly examined, and general features of a theoretical model of point defects are introduced. The specific theoretical and computational elements of a method bearing the acronym ICECAP are described. They consist of: (i) a quantum molecular defect cluster described in unrestricted Hartree-Fock self-consistent field approximation with Rayleigh-Schrödinger many-body perturbation theory correlation correction; (ii) a classical embedding crystal lattice represented by the shell model; (iii) a treatment of the cluster-lattice boundary condition derived from the Hartree-Fock description of the entire crystal, and including the Kunz-Klein localizing potential; (iv) the static lattice approximation; (v) atomic core pseudopotentials as an option; and (vi) the user-friendly program ICECAP that incorporates the preceding elements in a consistent variational treatment of the total defect lattice. Applications of the method to a number of systems are introduced with a description of several theoretical features that will arise, namely electronic localization and charge transfer, and basis-set and ion-size effects. Details are then given of analyses of the ground states of F centers and hydrogen in MgO and of the Vk center in LiF, the optical properties of Cu+ in NaF and of the F+ center in MgO, and the derivation and application of inter-ionic potentials for impurities and for perfect lattices. Finally, some comments are given regarding short-term and long-term application and development of the method. | ||||||
BibTeX:
@article{Vai1990,
author = {Vail, John M},
title = {Theory of electronic defects: Applications to MgO and alkali halides},
journal = {Journal of Physics and Chemistry of Solids},
year = {1990},
volume = {51},
number = {7},
pages = {589 - 607},
note = {ICECAP},
url = {http://www.sciencedirect.com/science/article/B6TXR-46PYNCW-59/2/596db647093d6189b81b7d9b2d3b6a50},
doi = {DOI: 10.1016/0022-3697(90)90139-7}
}
|
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| VaiCoiHeYan2002 | Vail, J.M.; Coish, W.A.; He, H. & Yang, A. | F center in $BaF2:$ Diffuse excited state | 2002 |
Phys. Rev. B Vol. 66 (1) , pp. 014109 |
article | |
| Abstract: The optical properties of the F center in BaF2 are of importance because the F center is a product of radiation damage when the material is used as a luminescent radiation detector. Its optical excitation energy is 2.03 eV, experimentally. We have applied computational modeling to study this process. Our method is based on a quantum molecular cluster containing the defect, embedded in a shell-model crystal. When the excess electron of the F center is kept localized in the molecular cluster, an excitation energy of 3.33 eV is found. When the F-center electron is allowed to become much more diffuse, the ground state remains within the vacancy, but the excited state delocalizes, and the excitation energy drops to about 2.56 eV, but the model is inaccurate because quantum-mechanical features of distant ions are omitted. A polaronic representation of the single diffuse electron is then carefully incorporated with the embedded quantum cluster treatment of the system. The polaron in BaF2 is found to be beyond the intermediate-coupling regime. Feynman’s path-integral results for Fröhlich’s polaron model give an effective mass of 3.12, in units of band mass. The resultant estimate of F-center excitation energy is 2.04 eV. The successful combination of a quantum molecular cluster modeling element with bulk crystal modeling elements (band mass and polaron correction) warrants further study along these lines. Quantitative and physical limitations of the method and results are discussed. | ||||||
BibTeX:
@article{VaiCoiHeYan2002,
author = {Vail, J. M. and Coish, W. A. and He, H. and Yang, A.},
title = {F center in $BaF2:$ Diffuse excited state},
journal = {Phys. Rev. B},
publisher = {American Physical Society},
year = {2002},
volume = {66},
number = {1},
pages = {014109},
note = {ICECAP},
doi = {http://dx.doi.org/10.1103/PhysRevB.66.014109}
}
|
||||||
| VaiHarHarSau1984 | Vail, J.M.; Harker, A.H.; Harding, J.H. & Saul, P. | Calculations for Electronic Point Defects with Self-Consistent Lattice Polarization - The $rm F^+$ Centre in MgO | 1984 |
Journal of Physics C: Solid State Physics Vol. 17 (19) , pp. 3401-3414 |
article | |
BibTeX:
@article{VaiHarHarSau1984,
author = {Vail, J M and Harker, A H and Harding, J H and Saul, P},
title = {Calculations for Electronic Point Defects with Self-Consistent Lattice Polarization -- The $rm F^+$ Centre in MgO},
journal = {Journal of Physics C: Solid State Physics},
year = {1984},
volume = {17},
number = {19},
pages = {3401-3414},
note = {ICECAP}
}
|
||||||
| VaiPanHar1987 | Vail, J.M.; Pandey, R. & Harker, A.H. | Simulation of F-Type Centres Using Hartree-Fock Clusters | 1987 |
Crystal Lattice Defects and Amorphous Materials Vol. 15 (1-4) , pp. 13-17 |
article | |
BibTeX:
@article{VaiPanHar1987,
author = {Vail, J M and Pandey, R and Harker, A H},
title = {Simulation of F-Type Centres Using Hartree-Fock Clusters},
journal = {Crystal Lattice Defects and Amorphous Materials},
year = {1987},
volume = {15},
number = {1-4},
pages = {13-17},
note = {ICECAP}
}
|
||||||
| VaiWoo1988 | Vail, J.M. & Woodward, C. | The ion-size effect for the F centre in NaF | 1988 |
Journal of Physics C: Solid State Physics Vol. 21 , pp. 3901-3907 |
article | |
| Abstract: One-electron calculations of the optical excitation energy of the F centre in NaF are carried out to test the applicability of norm-conserving pseudopotentials and Kunz-Klein localising potentials to represent the electronic structure of nearby ions. The calculations include consistent staticdistortion and polarisation derived from an infinite embedding shell-model lattice for the ground state. The basis set chosen for the wavefunction is optimised, and care is taken to avoid linear dependence. The results suggest that the electronic cores of nearby ions as determined in free-ion or perfect-lattice calculations are inadequate for the F centre. |
||||||
BibTeX:
@article{VaiWoo1988,
author = {Vail, John M and Woodward, Christopher},
title = {The ion-size effect for the F centre in NaF},
journal = {Journal of Physics C: Solid State Physics},
year = {1988},
volume = {21},
pages = {3901-3907},
note = {ICECAP}
}
|
||||||
| VelPanMar1994 | Veliah, S.; Pandey, R. & Marshall, S.A. | Modeling of defect properties of silver and its ions in alkali fluorides | 1994 |
Modelling and Simulation in Materials Science and Engineering Vol. 2 , pp. 933-938 |
article | |
| Abstract: Electron paramgnetic resonance studies have shown that the silver ion, A+. can act as a trap for both electrons and holes in irradiated alkali halide crystals, forming Ag0 and Ag2+ ions. In this paper we report the results of a simulation study using an embedded cluster approach. called ICECAP, thereby obtaining the ground state configuration and the charge stability of silver in the alkali fluorides, LiF, NaF, and KF. The ICECAP code combines the quantum cluster treated by the Hartree-Fock approximation and the embedding shell model lattice self-consistently. The calculations suggest that a Jahn-Teller distohon of the lattice will occur for the case of the Ag2+ ion, thereby causing the local environment of the ion to descend to tetragonal symmetry. The latter has been confirmed by an electron paramagnetic resonance (EPR) study for Ag doped in KF. |
||||||
BibTeX:
@article{VelPanMar1994,
author = {Veliah, Sunder and Pandey, Ravindra and Marshall , S A},
title = {Modeling of defect properties of silver and its ions in alkali fluorides},
journal = {Modelling and Simulation in Materials Science and Engineering},
year = {1994},
volume = {2},
pages = {933-938},
note = {ICECAP}
}
|
||||||
| ZuoPanKun1992 | Zuo, J.; Pandey, R. & Kunz, A.B. | Embedded Cluster Study of $rm Cu^+$ - Induced Lattice Relaxation in Alkali Halides | 1992 |
Physical Review B Vol. 45 , pp. 2709 |
article | |
BibTeX:
@article{ZuoPanKun1992,
author = {Zuo, J and Pandey, R and Kunz, A B},
title = {Embedded Cluster Study of $rm Cu^+$ - Induced Lattice Relaxation in Alkali Halides},
journal = {Physical Review B},
year = {1992},
volume = {45},
pages = {2709},
note = {ICECAP}
}
|
||||||
| ZuoPanKun1991 | Zuo, J.; Pandey, R. & Kunz, A.B. | Embedded Cluster Study of the Lithium Trapped Hole Center in Magnesium Oxide | 1991 |
Physical Review B Vol. 44 , pp. 7187 |
article | |
BibTeX:
@article{ZuoPanKun1991,
author = {Zuo, J and Pandey, R and Kunz, A B},
title = {Embedded Cluster Study of the Lithium Trapped Hole Center in Magnesium Oxide},
journal = {Physical Review B},
year = {1991},
volume = {44},
pages = {7187},
note = {ICECAP}
}
|
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