Structural and Thermodynamic Properties of Gallium Arsenide with Hexagonal Wurtzite Structure from First-Principles Analysis

A first-principles plane wave method with the ultrasoft pseudopotential
scheme in the frame of the generalized gradient approximation (GGA) is
performed to calculate the lattice parameters, the bulk modulus B ₀ and its pressure derivative B₀' of the hexagonal wurtzite GaAs (w-GaAs) by the Cambridge serial total energy package (CASTEP). Our calculations show that the most stable structure of the w-GaAs corresponds to the axial ratio c/a=1.651 and the internal parameter u= 0.374, consistent with other theoretical results. Also, the thermodynamic properties of the w-GaAs are investigated from the quasi-harmonic Debye model. The dependences of the normalized lattice parameters a/a₀, c/c₀, the axial ratio c/a, the normalized
volume V/V₀, the heat capacity C_v and the thermal expansion α on pressure P and temperature T are also obtained successfully.