通过焦点近似方法近似大基结合集群理论的振动频率
Philip M Nelson1, Zachary L Glick1, C David Sherrill1
1Center for Computational Molecular Science and Technology, School of Chemistry and Biochemistry, and School of Computational Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA.
焦点近似显著降低了高精度量子化学计算的计算成本. 这种方法准确地预测了分子频率,与传统的高级计算相比,可以节省大量时间.
科学领域:
- 计算化学的计算化学
- 量子化学 是一个量子化学.
- 频谱学是一种光谱学.
背景情况:
- 高精度的量子化学计算通常在计算上昂贵.
- 对分子振动频率的准确预测对于化学分析至关重要.
- 现有的方法,如合集群单元,双元和扰动三元[CCSD(T]提供高精度,但耗时.
研究的目的:
- 评估用于计算分子频率的焦点近似方法的性能.
- 将焦点方法的准确性和计算成本与标准高层计算进行比较.
- 评估焦点方法有效地接近完整基准集 (CBS) 极限的能力.
主要方法:
- 通过将第二阶级的莫勒-普莱塞特扰动理论 (MP2) 与CCSD (T) 结合起来,采用了焦点近似方法.
- 使用二次振动扰动理论 (VPT2) 计算了和基本振动频率.
- 与20个小分子 (最多6个原子) 的实验数据进行了对照,对焦点CCSD(T) 的结果进行了比较.
主要成果:
- 使用三次ζ基数组的焦点CCSD (T) 实现了与标准CCSD (T) 相比的精度,通过使用更大的基数组推断到使用完整基数组 (CBS) 极限.
- 与实验值相比,焦点方法对于基本频率的平均绝对误差仅为7.3厘米-1.
- 对于水 (H2O),焦点方法只需要额外推算CCSD的3%的计算时间,对于较大的分子来说预计会节省更多的时间.
结论:
- 焦点近似为高精度分子频率预测提供了一个计算高效的路线.
- 这种方法为标准的,资源密集的高层次量子化学计算提供了切实可行的替代方案.
- 焦点方法的成本效益预计会随着分子大小的增加而显著增加.
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