各位好！
在文献中看到对频率计算的分析，有这样一句话，Due to the negligence of anharmonicity effects and the approximate treatment of the electron correlation in DFT calculations, vibrational wavenumbers are typically larger than those
observed experimentally
请问anharmonicity effects 的物理意义是什么？它为何对计算频率产生影响？gaussian中如果使用freq=anhaanharmonicity 是否就已纠正了这种效应？谢谢！
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