Dipartimento di Chimica, Università di Parma, Viale Parco Area delle Scienze 17/A, I-43100 Parma, Italy.
J Chem Phys. 2012 Oct 21;137(15):154112. doi: 10.1063/1.4757285.
We present a new quantum chemical method for the calculation of the equilibrium geometry and the harmonic vibrational frequencies of molecular systems in dense medium at high pressures (of the order of GPa). The new computational method, named PCM-XP, is based on the polarizable continuum model (PCM), amply used for the study of the solvent effects at standard condition of pressure, and it is accompanied by a new method of analysis for the interpretation of the mechanisms underpinning the effects of pressure on the molecular geometries and the harmonic vibrational frequencies. The PCM-XP has been applied at the density functional theory level to diborane as a molecular system under high pressure. The computed harmonic vibrational frequencies as a function of the pressure have shown a satisfactory agreement with the corresponding experimental results, and the parallel application of the method of analysis has reveled that the effects of the pressure on the equilibrium geometry can be interpreted in terms of direct effects on the electronic charge distribution of the molecular solutes, and that the effects on the harmonic vibrational frequencies can be described in terms of two physically distinct effects of the pressure (curvature and relaxation) on the potential energy for the motion of the nuclei.
我们提出了一种新的量子化学方法，用于计算分子系统在高密度介质（高达 GPa 量级）中的平衡几何形状和简谐振动频率。新的计算方法命名为 PCM-XP，基于广泛用于标准压力条件下溶剂效应研究的极化连续体模型（PCM），并伴随着一种新的分析方法，用于解释压力对分子几何形状和简谐振动频率的影响机制。PCM-XP 已在密度泛函理论水平上应用于硼烷作为高压下的分子系统。计算得到的简谐振动频率随压力的变化与相应的实验结果吻合良好，同时应用分析方法揭示了压力对平衡几何形状的影响可以用分子溶质的电子电荷分布的直接作用来解释，而对简谐振动频率的影响可以用压力对核运动势能的两个物理上不同的作用（曲率和弛豫）来描述。
