On the utmost importance of the geometry factor of accuracy in the quantum chemical calculations of 31P NMR chemical shifts: New efficient pecG-n (n = 1, 2) basis sets for the geometry optimization procedure.

31P nuclear magnetic resonance (NMR) chemical shifts were shown to be very sensitive to the basis set used at the geometry optimization stage. Commonly used energy-optimized basis sets for a phosphorus atom containing only one polarization d-function were shown to be unable to provide correct equilibrium geometries for the calculations of phosphorus chemical shifts. The use of basis sets with at least two polarization d-functions on a phosphorus atom is strongly recommended.

What Most Affects the Accuracy of Te NMR Chemical Shift Calculations.

An accurate quantum chemical modeling of Te NMR spectra is of great importance in the NMR structural assignment for real-life tellurium compounds, which represent a growing interest in organic and inorganic chemistry nowadays. This work reports a computationally modest combined approach based on the density functional theory only, which provides an excellent accuracy against the experiment and can be effectively applied for the routine large-scale calculations of tellurium chemical shifts. The role of solvent, vibrational, and relativistic corrections has been thoroughly investigated.

Relativistic heavy atom effect on C NMR chemical shifts initiated by adjacent multiple chalcogens.

In this paper, we have investigated the cumulative peculiarity of the "heavy atom on light atom" effect on the C NMR chemical shifts, initiated by the adjacent chalcogens. For this purpose, the most accurate hybrid computational scheme for the calculation of chemical shifts of carbon nuclei, directly bonded with several heavy chalcogens, is introduced and attested on the representative series of molecules. The best hybrid scheme combines the nonrelativistic coupled cluster-based approach with the different types of corrections, including vibrational, solvent, and relativistic.

Algebraic-diagrammatic construction polarization propagator approach to indirect nuclear spin-spin coupling constants.

A new polarization propagator approach to indirect nuclear spin-spin coupling constantans is formulated within the framework of the algebraic-diagrammatic construction (ADC) approximation and implemented at the level of the strict second-order approximation scheme, ADC(2). The ADC approach possesses transparent computational procedure operating with Hermitian matrix quantities defined with respect to physical excitations. It is size-consistent and easily extendable to higher orders via the hierarchy of available ADC approximation schemes.