几种Mn+1AXn（n=1，2，3，etc.）纳米叠层的结构演化第一性原理加压陶瓷
Novel structural evolution of several nanolaminate Mn+1AXn (n=1, 2, 3, etc.) ceramics under pressure from first principles
摘要：
我们对典型的Mn+1AXn（n=1，2，3）纳米层状陶瓷的结构稳定性进行了深入的研究，发现Ti 2GaN的相变压力（160 GPa）远高于Zr 2GaN的（92 GPa），表明具有较强的M依赖性;而Zr 2AlN的相变压力（98 GPa）与Zr 2GaN的相变压力相近，表明具有较弱的A依赖性。在所有已知的MAX中，Mo 2GaC显示出最低的相变压力，这意味着含C相具有比含N相更低的相变压力。所选MAX的所有亚稳相几乎同时转变，例如Zr 2AlN的所有亚稳相在相似的压力（约90-110 GPa）下转变，具有小于20 GPa的非常窄的压力范围，对于Zr 2GaN对应于90-115 GPa和对于Mo 2GaC对应于10-25 GPa的情况也是如此。Mo 2GaC在高压下呈现多相共存状态，其P63/mmc α-β相变是这类MAX结构中较为常见和频繁发生的途径。六角P63-mmc到四角P4-mmm的转变是含氮MAX的常见直接途径，这可能是由于高的转变压力。P63/mmc α-β-P4-mmm转变可能是含C MAX的常见途径，这可能是由于α-β转变压力较低。Nb 2 InN（Nb 2GaN）和Mo 2 InN在低压下呈现c轴异常伸长，这些化合物在环境条件下具有负的能量形成，这意味着它们都是稳定的或可实验合成的。
英文摘要：
We did extensive research for the typical nanolaminate Mn+1AXn (n=1, 2, 3) ceramics focusing on the structural stability, the phase transition pressure of Ti2GaN (160 GPa) is far higher than that of Zr2GaN (92 GPa), meaning the strong M dependence of the same group, whereas Zr2AlN (98 GPa) has similar value with that of Zr2GaN, meaning the weak A dependence. Mo2GaC shows lowest phase transition pressure among all of the known MAX, meaning that C-containing phase has lower phase transition pressure than that of N-containing counterparts. All of the metastable phases of the selected MAX transition almost at the same time, such as all of the metastable phases of Zr2AlN transition at the similar pressure, about 90-110 GPa, with a very narrow pressure range of less than 20 GPa, as is also the case for Zr2GaN corresponding to 90-115 GPa and for Mo2GaC corresponding to 10-25 GPa. Mo2GaC presents multi-phase co-existence status at high pressure, whose P63/mmc alpha-beta phase transition is the more commonly and frequently occurred route in this kind of MAX structure. The hexagonal P63-mmc to tetragonal P4-mmm transition is the common direct route for the N-containing MAX due probably to the high transition pressure. P63/mmc alpha-beta-P4-mmm transition might be the common route for the C-containing MAX due probably to the low alpha-beta transition pressure. Nb2InN(Nb2GaN) and Mo2InN present c-axis abnormal elongation at low pressures, these compounds have negative formation of energy at ambient conditions, meaning that all of them are stable or experimentally synthesizeable.
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