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Lithium Fluoride

Crystal: LiF

Structure: NaCl

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Lattice formation energy:

-10.51 eV.

Lattice parameter:

2.008 Å at room temperature

 

(1.996 at 0K.)

Density:

2.646 g/cm3

 

Stiffness constants: in 1011 dynes/cm2, at room temperature

c11: 11.12 (12.46 at 0K.) (Ref. 1 & 2)

c12: 6.28 (6.49 at 0K.)

c44: 4.20 (4.24 at 0K.)

 

Compressibility (in 1011 dynes/cm2): 0.126 ??

 

Debye temperature: 735 K

Melting temperature: 1143 K

 

Phonon spectrum discussed by:

G. Dollings, H. G. Smith, R.M. Nicklow, R. Vigayaraghavan, M. K. Wilkinson, Lattice dynamics of Lithium Fluoride, Phys Rev. 168, 970 (1968)

 

Transverse optic phonon T0 (k=0): 307 or 318 cm-1

Longitude optic phonon L0 (k=0): 660 cm-1 (LST)

 

Gruneissen constant:

Ratio e*/e: 0.87

 

Photoelastic constants:

p11:

p12:

p44:

 

 

Band gap:

direct: eV. at K

indirect: eV. at ° K

 

 

Plasmon energy: 25 eV.

Exciton energy: 13.5 eV. (Ref.4) or 12.9 eV. (Ref.5)

Valence band: 6.1 eV. wide

 

Band structure discussed by:

A.B. Kunz, Self-consistant local orbitals for Lithium Halide Crystal, Phys Rev. B2, 2224 (1969)

See also Phys Rev. B13, 5540 (1976) for experiments

 

Static dielectric constant:

9.27 or 8.90 (Ref.6),

8.50 at 0K., 9.073 at 295K.(Ref.6),

8.547 at 15K. (Ref.6)

 

Optic dielectric constant: 1.92 or 1.90 (Ref.6), 1.93 at 0K.

See also Ref. 7 for T, P dependence

 

Electron mobility:

Hole mobility:

Polaron coupling constant: a = 6.4 ( for m*=1 )

Effective mass: conduction band:

valence band:

 

Electron affinity: ( in eV., from bottom of conduction band under vacuum)

1.8 eV. from colloid work (Jap.in)

4.12 eV. (Mott-Gurney, Ref.8), probably 3eV. too high

-1.8 eV. (Ping)

 

Spin-orbit coupling: ( valence band)

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Other information:

R.A. Verral, R.J. Fields and M.F. Ashby, Deformation-mechanism maps for LiF and NaCl, J. Am. Ceram. Soc. 60, 211 (1977)

 

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References:

 

  1. J.T. Lewis, A. Lehoczky & C.V. Briscoe, Elastic constants of the Alkali Halides at 4.2K Phys Rev. 161, 877 (1967)

    2.  

  2. L.E.A. Jones, High temperature behaviour of the elastic moduli of LiF & NaF: comparison with MgO & CaO Phys. Earth. I. 13, 105 (1976)

    3.  

  3. M. Piacentini, D.W. Linch & C.G. Olson, Thermoreflectance of LiF between 12 & 30 eV., Phys Rev. B13, 5530 (1976)

    4.  

  4. Journal de physique et du radium, 28 (1981)

    5.  

  5. W.B. Fowler, "Physics of Color Centers", New York: Academic Press (1968)

    6.  

  6. Digest of literature on Dielectrics. 2. Tables of Dielectric constants, 37, 18 (1973)

    7.  

  7. R.A. Bartells & A. Smith, Pressure & temperature dependence of the static dielectric constants of KCl, LiF& MgO Phys Rev. B7, 3887 (1973)

    8.  

  8. N.F. Mott & R.W. Gurney, "Electronic processes in Ionic crystals", 2nd. Edition (1950)

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