中文摘要：

采用第一性原理计算的方法研究了α/β-PbS的压力致相转变．计算了体系的键性质、电子能带结构和波恩有效电荷张量，通过分析压力下相对焓值变化得到转变压强9．6GPa．同时，计算了声子色散曲线和声子态密度，通过比较0和9．6GPa下的声子色散，发现在0和50cm^-1处出现了2个软模．结果表明，这2个软模在α/β-PbS的压致相变中起了重要的作用．

英文摘要：

In present work, first-principles calculations have been performed to study the pressure-induced phase transition of α/β-PbS. The bond properties, electronic band structures and BEC tensor are calculated. The transition pressure of 9.6 GPa is obtained through analysis of relative enthalpy with pressure. Moreover, the phonon dispersions and phonon density of states are calculated. Comparison of the phonon dispersions at 0 and 9.6 GPa reveals two soft TA phonon modes （ Eu and Blu）, between 0 and 50 cm^-1. It is noted that these two modes play an important role in understanding the atomic deviations in the α-PbS and the transformation to the β-PbS.