Four constant potential function of amorphous selenium and evaluation of its thermodynamic and acoustic properties

Abstract

Litov and Anderson after various considerations suggested a four constant potential function for a-Se as well as a-As₂S₃. Hence we also used a four constant potential function with the sole purpose of applying this potential function to obtain several acoustic, thermodynamic and other properties. We calculated several acoustic properties of a-Se like second order elastic constants (SOECs), their pressure derivatives, the longitudinal and transverse Gruneisen constant by two different methods, phonon frequencies, absorption band position through the use of Nath-Smith-Delaunay's equation, and the thermodynamic properties like heat capacity, bulk modulus, thermal Gruneisen constant, the pressure derivative of the bulk modulus (dK T/dP=C₁), the pressure derivative ofC 1 which is related to Anderson-Gruneisen parameter, pressure derivative of Gruneisen constant namely γ' _g which is related to second Gruneisen constant, characteristics of phonon frequencies, potential energy function through the use of fitted parameters and third order elastic constants. Finally we calculated K _T at the reduced density of ρ/ρ ₀=1.1.K _T is obtained from the potential function with the fitted parameters. In all the above cases the calculated values are found to be in good agreement with experiment wherever available. In this connection it is important to point out that we eliminated 'C' a constant in the potential function using the equilibrium condition as was done by Litovet al in a-Se and Gerlichet al in the case of a-As₂S₃ as all amorphous substances are isotropic as mentioned by several authors. We contemplate to calculate several other properties for a-Se and a-As₂S₃ and present them at a later stage.