自然轨道泛函理论中自旋多重态的解析梯度
Analytic gradients for spin multiplets in natural orbital functional theory
摘要：
本文用自然轨道泛函理论导出了非单线态化合物相对于核运动的解析能量梯度。我们利用多重态的公式，以获得一个简单的公式，适用于任何多电子系统在其地面混合态的总自旋S和所有可能的自旋投影Sz值。我们证明，可以得到分析梯度，而不诉诸线性响应理论或涉及迭代程序。它需要一个单一的评估，所以积分导数可以计算上的飞行沿计算，从而提高了有效性的筛选施瓦茨不等式。许多自旋多重性的小和中等大小的分子的结果显示。我们的结果与实验数据和精确的理论平衡几何进行了比较。
英文摘要：
Analytic energy gradients with respect to nuclear motion are derived for non-singlet compounds in the natural orbital functional theory. We exploit the formulation for multiplets in order to obtain a simple formula valid for any many-electron system in its ground mixed state with a total spin S and all possible spin projection Sz values. We demonstrate that the analytic gradients can be obtained without resorting to linear response theory or involving iterative procedures. It is required a single evaluation, so integral derivatives can be computed on-the-fly along the calculation and thus improve the effectiveness of screening by the Schwarz inequality. Results for small and medium size molecules with many spin multiplicities are shown. Our results are compared with experimental data and accurate theoretical equilibrium geometries.
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