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首页> 外文期刊>The Journal of Chemical Physics >Transferability of anharmonic force fields in simulations of molecular vibrations
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Transferability of anharmonic force fields in simulations of molecular vibrations

机译：分子振动模拟中非谐力场的传递性

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摘要

Accurate simulations of vibrational molecular spectra require precise molecular force fields, at least with cubic and quartic anharmonic corrections beyond the harmonic limits. Generation of such force field terms becomes computationally prohibitive for larger molecules. In this work, an alternate possibility is explored, where approximate anharmonic force field components are obtained from molecular fragments. Transferability properties of the cubic and incomplete quartic fields are discussed and tested on model oligoproline molecules. Automatic transfer schemes including cubic, two and three atomic quartic force constants are developed and implemented. The results indicate that the main vibrational interactions in molecules are local and the anharmonic constants are mostly well amendable to the transfer. Exact anharmonic normal mode force fields of larger molecules compared very well to those obtained from smaller molecular parts. The most important changes in vibrational spectra caused by the anharmonic interactions could be reproduced with two and three atomic force field terms. The transfer scheme thus provides molecular anharmonic force fields without a significant loss of accuracy and brings significant savings of computer time and memory needed to generate molecular vibrational energies and spectra.
机译：振动分子谱的精确模拟需要精确的分子力场，至少在三次和四次非谐波校正范围内要超出谐波极限。这样的力场项的产生对于较大的分子在计算上是禁止的。在这项工作中，探索了另一种可能性，其中从分子片段获得近似非谐力场分量。在模型寡聚脯氨酸分子上讨论并测试了三次和不完全四次场的可传递性。开发并实现了包括三次，二次和三次原子四次力常数的自动传输方案。结果表明，分子中的主要振动相互作用是局部的，并且非调和常数大部分可以很好地修正。与从较小分子部分获得的力场相比，较大分子的精确非谐正模力场非常好。由非谐相互作用引起的振动谱中最重要的变化可以用两个和三个原子力场项来再现。因此，转移方案可在不显着降低准确性的情况下提供分子非谐力场，并显着节省了计算机时间和生成分子振动能和光谱所需的内存。

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