Some aspects on thermodynamic properties, phase diagram and alloy formation in the ternary system BAs-GaAs - Part I: Analysis of BAs thermodynamic properties

Owing to the lack of available thermodynamic data based on experimental measurements of heat capacity, decomposition reaction or vapour pressure measurements, the problem of BAs stability is considered. We propose a new set of thermodynamic data for enthalpy of fort-nation, entropy and Gibbs free energy of Bas compound. By using thermodynamic database, our approach is based on the semiempirical trends and analogy in the variation of those quantities for several binary series in different III-V systems like arsenides, nitrides and phosphides. Thus, the values for BAs were derived by extrapolation from A1 to boron-based compounds (BAs, BP and, BN). For pure BAs(s), we predict a low enthalpy of formation in the standard state of Delta(f)H(0)(BAs) approximate to -30 kJ/mol at 300 K and a Gibbs free energy of Delta(f)G(0)(BAs) approximate to -40 +/- 5 kj/mol indicating a lower stability of this compound than GaAs. Those values are contradictory discussed with trends in the cohesive energy of several III-V systems. A cohesive energy of similar to 900 U/mol (9.4 eV) is proposed in agreement with Philips's rule. (c) 2006 Elsevier B.V. All rights reserved.