Ab initio molecular dynamics study of high-pressure melting of beryllium oxide

Abstract

We investigate, through first-principles molecular dynamics simulations, the high-pressure melting of BeO in the range 0 <= p <= 100 GPa. The wurtzite (WZ), zinc blend (ZB), and rocksalt (RS) phases of BeO are considered. It is shown that below 40 GPa, the melting temperature for the WZ phase is higher than that for the ZB and RS phases. When the pressure is beyond 66 GPa, the melting temperature for the RS phase is the highest one, in consistent with the previously reported phase diagram calculated within the quasiharmonic approximation. We find that in the medium pressure range between 40 to 66 GPa, the ZB melting data are very close to those of RS, which results from the fact that the ZB structure first transforms to RS phase before melting. The ZB-RS-liquid phase transitions have been observed directly during the molecular dynamics runs and confirmed using the pair correlation functions analysis. In addition, we propose the melting curve of BeO in the form T-m = 2696.05 (1 + P/24.67)(0.42), the zero-pressure value of 2696.05 K falling into the experimental data range of 2693 similar to 2853 K.