Improved modelling of liquid GeSe$_2$: the impact of the exchange-correlation functional

TL;DR

This study uses first-principles molecular dynamics with the BLYP exchange-correlation functional to improve the modeling of liquid GeSe$_2$, showing enhanced agreement with experimental data and revealing detailed structural properties.

Contribution

It demonstrates that the BLYP functional significantly improves the accuracy of structural predictions for liquid GeSe$_2$ over previous PW-based approaches.

Findings

BLYP yields more structured Ge$-$Ge pair correlation functions.

Increased tetrahedral order observed with BLYP.

Diffusion coefficients are an order of magnitude smaller with BLYP.

Abstract

The structural properties of liquid GeSe$_2$ are studied by using first-principles molecular dynamics in conjuncton with the Becke, Lee, Yang and Parr (BLYP) generalized gradient approximation for the exchange and correlation energy. The results on partial pair correlation functions, coordination numbers, bond angle distributions and partial structure factors are compared with available experimental data and with previous first-principle molecular dynamics results obtained within the Perdew and Wang (PW) generalized gradient approximation for the exchange and correlation energy. We found that the BLYP approach substantially improves upon the PW one in the case of the short-range properties. In particular, the Ge$-$Ge pair correlation function takes a more structured profile that includes a marked first peak due to homopolar bonds, a first maximum exhibiting a clear shoulder and a deep minimum, all these features being absent in the previous PW results. Overall, the amount of tetrahedral order is significantly increased, in spite of a larger number of Ge$-$Ge homopolar connections. Due to the smaller number of miscoordinations, diffusion coefficients obtained by the present BLYP calculation are smaller by at least one order of magnitude than in the PW case.