Improved modeling of liquidGeSe2: Impact of the exchange-correlation functional

Abstract

The structural properties of liquid ${\text{GeSe}}_{2}$ are studied by using first-principles molecular dynamics in conjunction 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-principles 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.