Neopentane and TMS are used as model M(CH(3))(4) systems to investigate intramolecular interactions. The nonbonded site-site potential between two proximal hydrogen atoms on different methyl groups, V(nb)(d(HH)), is not Lennard-Jones- or Morse-like but is found to be pseudolinear in hydrogen-hydrogen internuclear separation, d(HH), for both neopentane and TMS. The Morse potential is found to be a poor basis in which to expand V(nb)(d(HH)). The nonbonded site-site potential is conformation-dependent and not transferable between molecules. The individual contributions to V(nb)(d(HH)) are presented. The local mode parameters for neopentane and TMS are calculated ab initio for a variety of molecular conformations. The ab initio values of the local mode frequency and local mode anharmonicity are increasingly blue-shifted with increasing steric hindrance. Electron correlation is found to be increasingly important with decreasing internuclear separations, d(HH).

中文翻译：

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新戊烷和四甲基硅烷中的位点电位。

新戊烷和TMS用作模型M（CH（3））（4）系统来研究分子内的相互作用。V（nb）（d（HH））上不同甲基上的两个近端氢原子之间的非键合位点电位不是Lennard-Jones或Morse样的，但在氢氢原子核分离中被发现是伪线性的， d（HH），对于新戊烷和TMS而言。发现摩尔斯电势是扩展V（nb）（d（HH））的基础不佳。非结合位点-位点电位是构象依赖性的，并且不能在分子之间转移。列出了对V（nb）（d（HH））的各个贡献。从头开始计算各种分子构象的新戊烷和TMS的局部模式参数。本地模式频率和本地模式非谐波的从头算值随着空间位阻的增加而蓝移。随着核间距d（HH）的减小，电子相关性变得越来越重要。