Compound semiconductor alloys have been the focus of research as materials of construction for optoelectronic devices. The miscibility of these alloys is difficult to quantify experimentally. The literature data available, from theoretical modelling studies using the regular solution theory, shows wide variance. Hence, in this study, the molecular simulation approach is used with empirical Valence Force Field potential model to predict the miscibility diagrams, critical state properties and critical exponents for semiconductors. Simulation results indicate AlxGa1-xAs, AlxGa1-xP and AlxGa1-xSb alloys are completely miscible at room temperature. For the other alloys, the miscibility diagram is asymmetric and the upper critical solution temperature (UCST) increases as the lattice mismatch increases. At a temperature below UCST, wide miscibility gap exists and phase segregation occurs. The critical exponents, alpha(C) and beta(C), calculated are found to be in good agreement with known solution values. (C) 2011 Elsevier B.V. All rights reserved.