Estimation of structural parameters of Germanium-Carbon alloy system using cluster variation method

Collaborators: Mr. K. Shiva Shankar, Ms. Rekha T, Mr. Shanmukha Reddy, Dr. Srinivasa Gupta G

Overview

The experimental determination of phase diagrams is a time-consuming and costly task that becomes even more pronounced as the number of components increases. The Cluster Variation Method (CVM) is a refined method to determine the phase diagrams that considers the multi-atom interactional effects (sub-clusters within the main cluster), vibrational energies, and structural parameters thereby giving more accurate and reliable results compared to existing techniques.

The CVM approximates the joint probability distribution by several (overlapping) marginal distributions (clusters). The quality of the approximation is determined by the size and number of clusters. For this project, a triangle has been used as the base cluster and accordingly, the correlation functions were calculated which depend on the composition of an alloy. This was followed up by calculating the entropy of the system, and then the Gibbs free energy. The Gibbs free energy was then minimized using the Newton-Raphson method. All the calculations were performed using Mathematica software and the resulting phase diagrams were compared with Thermo-Calc software.