Performance of GESC and LRESC models for heavy-atom nuclear magnetic shieldings

• Autores: Zapata Escobar, Andy Danian; Melo, Juan Ignacio; Aucar, Gustavo Adolfo
• Año de publicación: 2025
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: LRESC; GESC; Shielding; Polarization Propagator
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Some models have been developed recently to calculate and analyze the electronic origin of the nuclear magnetic shielding tensor. We present here the most recent results of calculations performed with the Geometric Elimination of the Small Component (GESC) model, which represents a partial improvement of the Linear Response Elimination of the Small Component (LRESC) model, particularly concerning diamagnetic contributions. We have found that the accuracy of the diamagnetic contributions obtained with the GESC model is higher than the one obtained with the LRESC model for any molecular system. The difference between the LRESC (σLRESCd) and the four-component (σpp) methods is mainly due to the Fermi contact mechanism (σFC,LRESC). In the case of the GESC model, the contribution of such electronic mechanism is lowered by a factor of 5/7 with respect to σ pp. Furthermore, the next important mechanism that contributes to the differences between σdLRESC and σpp is known as DiaK (σDiaK), being its values close to half of that due to σFC,LRESC. We analyze here the electronic mechanisms involved in the NMR shielding of halogen atoms of the following family of compounds: HX, IX, and AtX, where X = H, F, Cl, Br, I, At, and the shielding of the central atoms in the following family of molecules: Sn4−iXi and PbH4−iXi with i = 1–4 and X = H, F, Cl, Br, I. The calculations were performed at the LRESC-HF/DFT and GESC-HF/DFT levels of theory together with four-component DHF.
Fil: Zapata Escobar, Andy Danian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Modelado e Innovación Tecnológica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovación Tecnológica; Argentina
Fil: Melo, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina
Fil: Aucar, Gustavo Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Modelado e Innovación Tecnológica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovación Tecnológica; Argentina