arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2104.14673physics.chem-ph
收藏

基于约束核电子轨道密度泛函理论解析Hessian的分子振动频率

Molecular vibrational frequencies from analytic Hessian of constrained nuclear-electronic orbital density functional theory

Xi Xu, Yang Yang

摘要:

核量子效应在各种化学和生物过程中是重要的。约束核电子轨道密度泛函理论(cNEO-DFT)已发展到包括能量表面中的核量子效应。在这里,我们开发了cNEO-DFT能量相对于核(期望)位置的变化的解析Hessian,它可以用来表征能量表面上的驻点和计算分子的振动频率。这是通过构造和求解多组分cNEO耦合扰动Kohn-Sham(cNEO-CPKS)方程来实现的,该方程描述了电子和核轨道对核(预期)位置位移的响应。与解析Hessian,一系列的小分子的振动频率的计算和比较,从传统的DFT Hessian计算,以及那些从振动二阶微扰理论(VPT 2)。结果发现,即使与谐波处理,cNEO-DFT显着优于DFT和DFT-VPT 2在描述的振动频率在规则的多原子分子。此外,cNEO-DFT可以合理地描述具有共享质子的系统中的质子转移模式,而DFT-VPT 2通常面临很大的挑战。我们的研究结果表明核量子效应在分子振动中的重要性,cNEO-DFT是一种精确而廉价的描述分子振动的方法。

英文摘要:

Nuclear quantum effects are important in a variety of chemical and biological processes. The constrained nuclear-electronic orbital density functional theory (cNEO-DFT) has been developed to include nuclear quantum effects in energy surfaces. Herein we develop the analytic Hessian for cNEO-DFT energy with respect to the change of nuclear (expectation) positions, which can be used to characterize stationary points on energy surfaces and compute molecular vibrational frequencies. This is achieved by constructing and solving the multicomponent cNEO coupled-perturbed Kohn-Sham (cNEO-CPKS) equations, which describe the response of electronic and nuclear orbitals to the displacement of nuclear (expectation) positions. With the analytic Hessian, the vibrational frequencies of a series of small molecules are calculated and compared to those from conventional DFT Hessian calculations as well as those from the vibrational second-order perturbation theory (VPT2). It is found that even with a harmonic treatment, cNEO-DFT significantly outperforms DFT and is comparable to DFT-VPT2 in the description of vibrational frequencies in regular polyatomic molecules. Furthermore, cNEO-DFT can reasonably describe the proton transfer modes in systems with a shared proton, whereas DFT-VPT2 often faces great challenges. Our results suggest the importance of nuclear quantum effects in molecular vibrations, and cNEO-DFT is an accurate and inexpensive method to describe molecular vibrations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑