Scalar Relativistic Computations of Nuclear Magnetic Shielding and g-Shifts with the Zeroth-Order Regular Approximation and Range-Separated Hybrid Density Functionals

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• 作者：Fredy Aquino ; Niranjan Govind ; Jochen Autschbach
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2011
• 出版时间：October 11, 2011
• 年：2011
• 卷：7
• 期：10
• 页码：3278-3292
• 全文大小：1056K
• 年卷期：v.7,no.10(October 11, 2011)
• ISSN：1549-9626

文摘

Density functional theory (DFT) calculations of NMR chemical shifts and molecular g tensors with Gaussian-type orbitals are implemented via second-order energy derivatives within the scalar relativistic zeroth order regular approximation (ZORA) framework. Nonhybrid functionals, standard (global) hybrids, and range-separated (Coulomb-attenuated, long-range corrected) hybrid functionals are tested. Origin invariance of the results is ensured by use of gauge-including atomic orbital (GIAO) basis functions. The new implementation in the NWChem quantum chemistry package is verified by calculations of nuclear shielding constants for the heavy atoms in HX (X = F, Cl, Br, I, At) and H₂X (X = O, S, Se, Te, Po) and ¹²⁵Te chemical shifts in a number of tellurium compounds. The basis set and functional dependence of g-shifts is investigated for 14 radicals with light and heavy atoms. The problem of accurately predicting ¹⁹F NMR shielding in UF_6鈥?i>nCl_n, n = 1鈥?, is revisited. The results are sensitive to approximations in the density functionals, indicating a delicate balance of DFT self-interaction vs correlation. For the uranium halides, the range-separated functionals are not clearly superior to global hybrids.