GaP - Gallium Phosphide

Mechanical properties, elastic constants, lattice vibrations

Basic Parameter
Elastic constants
Acoustic Wave Speeds
Phonon frequencies

Basic Parameter

Bulk modulus 8.8·1011 dyn/cm2
Density 4.138 g/cm3
Hardness 5 on the Mohs scale
Surface microhardness (using Knoop's pyramid test) 850 kg/mm2
Cleavage plane { 110 }
Piezoelectric constant e14= -0.1 C m-2

Elastic constants

C11 = 14.05·1011 dyn/cm2
C12 = 6.20·1011 dyn/cm2
C44 = 7.03·1011 dyn/cm2
(Yogurtcu et al. [1981]).
Temperature dependences of elastic constants.
(Boyle and Sladek [1975]).

For 300 K

Bulk modulus (compressibility-1) Bs = 8.82·1011 dyn/cm2
Shear modulus C' = 3.92·1011 dyn/cm2
[100] Young's modulus Yo= 10.3·1011 dyn/cm2
[100] Poisson ratio σo = 0.31

Acoustic Wave Speeds

Wave propagation Direction Wave character Expression for wave speed Wave speed (in units of 105 cm/s)
[100] VL (C11/ρ)1/2 5.83
VT (C44/ρ)1/2 4.12
[100] Vl [(C11+Cl2+2C44)/2ρ]1/2 6.43
Vt|| Vt||=VT=(C44/ρ)1/2 4.12
Vt⊥ [(C11-C12)/2ρ]1/2 3.08
[111] Vl' [(C11+2C12+4C44)/3ρ]1/2 6.63
Vt' [(C11-C12+C44)/3ρ]1/2 3.46

Phonon frequencies (in units of 1012 Hz) T=4.2 K

νLO(X) 11.3
νTO(X) 10.96
νLA(X) 7.65
νTA(X) 3.16
(Suto and Nashizawa [1990])