Jakubowska Katarzyna, Pecul Magdalena, Ruud Kenneth
Faculty of Chemistry, University of Warsaw, 02-093 Warsaw, Poland.
Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, UiT - The Arctic University of Norway, N-9019 Tromsø, Norway.
J Phys Chem A. 2021 Dec 9;125(48):10315-10320. doi: 10.1021/acs.jpca.1c07398. Epub 2021 Nov 29.
We investigate the effect of relativity on harmonic vibrational frequencies. Density functional theory (DFT) calculations using the four-component Dirac-Coulomb Hamiltonian have been performed for 15 hydrides (HX, X = O, S, Se, Te, Po; XH, X = N, P, As, Sb, Bi; and XH, X = C, Si, Ge, Sn, Pb) as well as for HC≡CPbH. The vibrational frequencies have been calculated using finite differences of the molecular energy with respect to geometrical distortions of the nuclei. The influences of the choice of basis set, exchange-correlation functional, and step length for the numerical differentiation on the calculated harmonic vibrational frequencies have been tested, and the method has been found to be numerically robust. Relativistic effects are noticeable for the heavier congeners HTe and HPo, SbH and BiH, and SnH and PbH and are much more pronounced for the vibrational modes with higher frequencies. Spin-orbit effects constitute a very small fraction of the total relativistic effects, except for HTe and HPo. For HC≡CPbH we find that only the frequencies of the modes with large contributions from Pb displacements are significantly affected by relativity.
我们研究相对论对谐波振动频率的影响。使用四分量狄拉克 - 库仑哈密顿量进行了密度泛函理论（DFT）计算，对象包括15种氢化物（HX，X = O、S、Se、Te、Po；XH，X = N、P、As、Sb、Bi；以及XH，X = C、Si、Ge、Sn、Pb）和HC≡CPbH。振动频率通过分子能量相对于原子核几何畸变的有限差分来计算。测试了基组选择、交换相关泛函以及数值微分步长对计算得到的谐波振动频率的影响，发现该方法在数值上是稳健的。对于较重的同系物HTe和HPo、SbH和BiH以及SnH和PbH，相对论效应较为明显，并且对于频率较高的振动模式更为显著。除了HTe和HPo，自旋 - 轨道效应在总相对论效应中占比非常小。对于HC≡CPbH，我们发现只有那些来自Pb位移贡献较大的模式的频率受到相对论的显著影响。
