一水合氨高压离子和分子晶体的密度泛函理论
High pressure ionic and molecular crystals of ammonia monohydrate within density functional theory
摘要：
结合第一性原理密度泛函理论计算和结构搜索预测了一水氨质子转移改性的稳定性，空间群为P4/nmm。用PBE密度泛函计算了相图，并研究了半经验色散校正、零点运动和有限温度的影响。与MP2和耦合簇计算的比较表明，PBE功能过稳定的质子转移阶段，因为太多的电子电荷移动的质子。这种过度结合通过使用PBE 0混合交换相关泛函部分校正，其相对于一水合氨（AMH-I）的相I使P4/nmm的焓每化学式单位增加约0.6eV，并将质子转移相的转变从2.8GPa的PBE压力转移到约10 GPa。这与实验一致，因为在高达~9 GPa的压力下尚未观察到质子转移阶段，而更高的压力尚未在实验中探索。
英文摘要：
A combination of first-principles density functional theory calculations and a search over structures predicts the stability of a proton-transfer modification of ammonia monohydrate with space group P4/nmm. The phase diagram is calculated with the PBE density functional, and the effects of a semi-empirical dispersion correction, zero point motion, and finite temperature are investigated. Comparison with MP2 and coupled cluster calculations shows that the PBE functional over-stabilizes proton transfer phases because too much electronic charge moves with the proton. This over-binding is partially corrected by using the PBE0 hybrid exchange-correlation functional, which increases the enthalpy of P4/nmm by about 0.6 eV per formula unit relative to phase I of ammonia monohydrate (AMH-I) and shifts the transition to the proton transfer phase from the PBE pressure of 2.8 GPa to about 10 GPa. This is consistent with experiment as proton transfer phases have not been observed at pressures up to ~9 GPa, while higher pressures have not yet been explored experimentally.
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