_____________________________________________________________________
Information on TiO
_____________________________________________________________________
New models for the positive and negative temperature coefficients of resistivity for TiO(0.80-1.23) metallic oxides.
D.S. McLachlan Phys. Rev. B25, 2285 (1982)
A reexamination is made of previous resistivity data of the TiO(0.80-1.23) metallic oxide system, in which very large positive and negative temperature coefficients of resistivity
a are observed.TiO(0.80-1.23) samples contain a large number of stoichiometric vacancies which can be thermally ordered and disordered, drastically changing the residual resistivity, without seriously affecting the superconducting Tc. Fitting the results to the two-level model shows that any resistivity due to the two-level system must operate in parallel with the normal electron-phonon interactions. A phenomenological formula, based on the ideas of incipient localisation in very-high-resistivity materials, is introduced. This formula fits all the data for the TiO(0.80-1.23) system in a semiquantitative way. It also predicts that a zero
a (the Mooij criterion) occurs when the elastic mean free path and the weak localisation coherence length are approximately equal.
Comments on "Significant differences between Hartree-Fock and local-exchange energy bands for TiO"
S. and A. Neckel Phys. Rev. B19, 5439 (1979)
The recent controversy over the bonding in TiO, particularly with respect to O-2p-Ti-3d band overlap, is re-examined. The soft-x-ray emission spectra (SXS) are recalculated within the X
a formalism and agree well with experimental results. The XPS data are discussed and it is found that discrepancies between theory and experiment exist for both the Xa and Hartree-Fock calculations. From the SXS and XPS spectra it is concluded that the O-2o-Ti-3d mixing is better represented by the Xa band structure.
Comment on "Significant differences between Hartree-Fock and local exchange energy bands for TiO"
K. Schwarz and A. Neckel Phys. Rev. B19, 5439 (1979)
The recent statement of Jennison and Kunz that "if present indication continue...one would be forced to conclude that the X
a method is not applicable to TiO" is shown to be based on a number of misinterpretations and omissions. The nominal TiO in the x-ray photoelectron spectrum (XPS) upon which they rely heavily has almost certainly suffered surface oxidation. They have also not given proper consideration to the x-ray emission spectra (XES) to TiO, which show a separation of the local density of states (DOS) maxima of O-2p and Ti-3d type of about 5-6 eV.
Significant differences between Hartree-Fock and local-exchange energy bands for TiO. A reply
A.B. Kunz
The previous calculation of the Hartree-Fock energy bands of TiO by Jennison and Kunz (Ref. Phys.Rev.Letters 39, 418 (1977)) is subjected here to correlation corrections. These corrections include the long-range screening due to the low-density of conduction electrons and also the polarization of the ion cores inside the screening radius. These corrections reduce the occupied valence bandwidth to 8.3 eV, increase the separation of the centre of the d-band density of states maximum to the centre of the p-band density of states maximum to 4.8 eV and reduces the density of states in the region between the d-band and p band peaks to a clear minimum which is however nonzero. The correlation effects reduce the p-d overlaps to a value of 1.3 eV, from a Hartree-Fock value of 4.4 eV.
_____________________________________________________________________