Mass Spectrometric Study of the GaAs System

The vaporization of GaAs has been investigated by means of the mass spectrometric method. The activity values of the components were determined in a composition range of 50–95 at.% Ga at 1283°K. The heteronuclear gaseous species GaAs was detected by the aid of double‐oven experiments. Its dissociation energy ${\mathrm{D°}}_{298}\text{\hspace{0.17em}=\hspace{0.17em}50.1\hspace{0.17em}±\hspace{0.17em}0.3}{\mathrm{kcal\; mole}}^{\text{−1}}$ was determined using the third‐law method. The equilibrium reaction As₄⇋2As₂ was considered in the study of the vapor over GaAs. Second‐law and third‐law values ${\mathrm{D°}}_{298}\text{\hspace{0.17em}=\hspace{0.17em}77\hspace{0.17em}±\hspace{0.17em}5}$ and 73.5 ± 0.3 kcal mole⁻¹, respectively, for the As₂–As₂ bond were obtained. The value ${\mathrm{D°}}_{298}\text{\hspace{0.17em}=\hspace{0.17em}71.0\hspace{0.17em}±\hspace{0.17em}3.0}{\mathrm{kcal\; mole}}^{\text{−1}}$ is proposed as a result of comparison with previous determinations.