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Zeroth order regular approximation approach to parity violating nuclearmagnetic resonance shielding tensors

机译：零次正则逼近核磁共振屏蔽张量的奇偶性方法

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摘要

In this paper, a quasirelativistic two-component zeroth order regular approximation (ZORA) densityfunctional theory (DFT) approach to the calculation of parity violating (PV) resonance frequencydifferences between the nuclear magnetic resonance (NMR) spectra of enantiomers is presented andthe systematics of PV NMR shielding constants in C_2-symmetric dihydrogen dichalcogenides (H_2X_2with X=~(17)O, ~(33)S,~(77)Se, 125)Te,~(209)Po)are investigated. The typical sin(2α)-like dependence of thePV NMR frequency splittings on the dihedral angle a is observed for the entire series. As for thescaling behavior of the effect with the nuclear charge Z of X, the previously reported Z~(2.5± 0.5)scalingin the nonrelativistic limit is reproduced and a scaling of approximately Z~3for the paramagnetic andZ~5for the spin-orbit coupling contribution to the frequency splitting is observed in the relativisticframework. The paramagnetic and spin-orbit coupling contributions are typically of opposite signfor the molecular structures studied herein and the maximum scaling of the total ZORA frequencysplitting (i.e., the sum of the two contributions) is Z~(3.9)for H_2Po_2. Thus, an earlier claim aspin-orbit coupling contribution scaling with up to Z~7for H_2Po_2and the erratic dihedral angledependence obtained for this compound within a four-component Dirac–Hartree–Fock–Coulombstudy is not confirmed at the DFT level. The maximum NMR frequency splitting reported here is ofthe order of 10 mHz for certain clamped conformations of H_2Po_2inside a static magnetic field withmagnetic flux density of 11.7 T. Frequency splittings of this size have been estimated to bedetectable with present day NMR spectrometers. Thus, a NMR route toward molecular PV appearspromising once suitable compounds have been identified.
机译：本文提出了一种拟对偶性的零分量零阶正则逼近（ZORA）密度泛函理论（DFT）方法来计算对映异构体的核磁共振（NMR）谱之间的奇偶违反（PV）共振频率差，并建立了PV体系研究了C_2对称的二氢二氢二硫化物（H_2X_2，X =〜（17）O，〜（33）S，〜（77）Se，125）Te，〜（209）Po）的NMR屏蔽常数。在整个序列中观察到PV NMR频率分裂对二面角α的典型sin（2α）状依赖性。关于X的核电荷Z的效应的缩放行为，再现了先前报道的非相对论极限中的Z〜（2.5±0.5）缩放，顺磁的缩放比例约为Z〜3，自旋轨道耦合的缩放比例约为Z〜5。在相对论框架中观察到频率分裂。对于本文研究的分子结构，顺磁性和自旋轨道耦合贡献通常具有相反的符号，并且对于H_2Po_2，总ZORA分频的最大比例（即，两个贡献的总和）为Z〜（3.9）。因此，在DFT层级上未确认较早的声称H_2Po_2高达Z〜7的Aspin-轨道耦合贡献定标，以及该化合物在四组分Dirac–Hartree–Fock–Coulombstudy中获得的不稳定的二面角依赖性。此处报道的最大NMR频率分裂在一定的H_2Po_2固定构象下在磁通密度为11.7 T的静磁场中约为10 mHz。在目前的NMR光谱仪中，估计可以检测到这种大小的频率分裂。因此，一旦鉴定出合适的化合物，向分子PV的NMR途径就有望出现。

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