【摘要】 采用不同的第一性原理方法计算H₂S在140¹60GPa的3个稳定结构P-1,C2/m,Cmca的形成焓,发现这3个结构的形成焓非常接近,平均每个原子的焓差不足2meV,基本具有同样的热力学稳定性,表明硫化氢在这段压强内可能会存在多相共存。在此基础上研究了P-1结构转变到C2/m结构和C2/m结构转变到Cmca结构的相变结构和相变势垒。发现P-1结构到C2/m结构的相变只是H3原子位置的变化,其相变势垒只有0.02meV,表明H3原子在P-1结构和C2/m结构相变时H3原子可以自由的波动,P-1结构相变到C2/m结构非常容易,可能存在着质子的量子隧穿效应。通过扭曲H4S6单元模拟C2/m结构到Cmca结构的相变过程,其势垒与P-1结构到C2/m结构的势垒相比,C2/m结构通过这种方式转变到Cmca结构所需的相变势垒相对较高,值约为每一个H2S单元250meV。更多还原

【Abstract】 The formation enthalpy of P-1,Cmca and C2/m structures at 140-160 GPa is calculated by using different first-principle methods.It is found that the enthalpy of formation of these three structures is very close,and the average enthalpy difference of each atom is less than 2 meV,which shows the same thermodynamic stability.It is suggested that the structure of H2 S may coexist in multiphase at this pressure.The transition barrier of P-1 structure to C2/m structure and C2/m structure to Cmca structure are further studied.The phase transition barrier of P-1 structure to C2/m structure is only 0.02 meV,and the H3 proton can fluctuate freely during the two phase transition process.The quantum tunneling effect of protons may exist.The phase transition barrier of C2/m structure transits to Cmca structure is simulated by twisting H4 S6 rectangular units and the value is about 250 meV per H2 S unit,which is relatively higher than that of P-1 structure to C2/m structure.更多还原