Mg2C高压性质的从头计算法研究

运用基于密度泛函理论的平面波赝势方法，结合广义梯度近似，系统地研究了Mg2C在高压下的结构相变、电子结构和光学性质。计算结果表明Mg2C在高压下将发生两次相变，一次是从反萤石到反氯化铅结构的一阶相变在30.09 GPa，另一次是从反氯化铅结构到Ni2In型结构的二阶相变在260 GPa。此外，对压力下电子结构和光学性质的分析表明，Mg2C的带隙宽度随着压力增加而增加，与Mg2Si在压力下表现出金属性有很大不同。

The phase transitions, electronic structures and optical properties of Mg2C under pressure: Ab-initio calculations

The phase transitions, electronic structures and optical properties of Mg2C were investigated using the first-principles plane-wave method within the pseudopotential and generalized gradient approximations. The calculated results demonstrate that Mg2C undergoes two pressure-induced phase transitions: one is a first-order phase transition from the anti-fluorite structure to the anti-cotunnite structure at 20.09 GPa, and the other is a second-order phase transition from the anti-cotunnite structure to the Ni2In-type structure at 260 GPa. Moreover, the electronic and optical properties of Mg2C under pressure were discussed; they show that the band gaps become broader with the increase of the pressure. This is different from Mg2Si, which has become metallic at high pressure.