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First principles prediction of isotopic shifts in H_2O

机译：H_2O同位素位移的第一性原理预测

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We compute isotope-independent first-and second-order corrections to the Born-Oppenheimer approximation for water and use them to predict isotopic shifts. For the diagonal correction,we use internally contracted multireference configuration interaction wave functions and derivatives with respect to mass-dependent internal coordinates to generate the mass-independent correction function. For the nonadiabatic correction,we use a self-consistent field wave function for the ground electronic state and single excitation configuration interaction wave functions for the excited states and a generalization of the handy,Yamaguchi,and Schaefer method to obtain mass-independent correction functions. We find that including the nonadiabatic correction gives significantly improved results compared to just including the diagonal correction when the Born-Oppenheimer potential energy surface is optimized for H_2 ~(16)O.The agreement with experimental results for deuterium-and tritium-containing isotopes is nearly as good as our best empirical correction,however,the present correction is expected to be more reliable for higher,uncharacterized,levels.
机译：我们对水的Born-Oppenheimer近似计算独立于同位素的一阶和二阶校正，并使用它们来预测同位素的变化。对于对角线校正，我们使用内部收缩的多参考配置交互波函数和关于质量相关的内部坐标的导数来生成质量无关的校正函数。对于非绝热校正，我们对基态电子状态使用自洽场波函数，对激发态使用单激发配置相互作用波函数，并对方便，山口和Schaefer方法进行了推广，以获得与质量无关的校正函数。我们发现，当仅将Born-Oppenheimer势能面优化为H_2〜（16）O时，与仅包括对角线校正相比，包括非绝热校正可以显着改善结果。与氘和tri同位素的实验结果相符但是，与更高的经验值几乎一样，不过，对于更高的，没有特征的水平，当前的校正方法将更加可靠。

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