Atomic Shielding Constants

Nuclear shielding constants by density functional theory with gauge including atomic orbitals

Recently, we introduced a new density-functional theory ~DFT! approach for the calculation of NMR shielding constants. First, a hybrid DFT calculation ~using 5% exact exchange! is performed on the molecule to determine Kohn–Sham orbitals and their energies; second, the constants are determined as in nonhybrid DFT theory, that is, the paramagnetic contribution to the constants is calculated from...

Predicting shielding constants in solution using gauge invariant atomic orbital theory and the effective fragment potential method.

A method to approximate ab initio shielding constants is presented, in which the ab initio density matrix is replaced in the gauge invariant atomic orbital formalism with the density matrix resulting from an effective fragment potential calculation. The resulting first-order density matrix is then iterated to self-consistency. The method is compared with fully ab initio gauge invariant atomic o...

Spin-rotation and NMR shielding constants in HCl.

The spin-rotation and nuclear magnetic shielding constants are analysed for both nuclei in the HCl molecule. Nonrelativistic ab initio calculations at the CCSD(T) level of approximation show that it is essential to include relativistic effects to obtain spin-rotation constants consistent with accurate experimental data. Our best estimates for the spin-rotation constants of (1)H(35)Cl are CCl = ...

Calculation of Nuclear Magnetic Shielding Constants in Two Simple Systems

Natural chemical shielding analysis of nuclear magnetic resonance shielding tensors from gauge-including atomic orbital calculations

Nuclear magnetic shielding tensors computed by the gauge including atomic orbital ~GIAO! method in the Hartree–Fock self-consistent-field ~HF-SCF! framework are partitioned into magnetic contributions from chemical bonds and lone pairs by means of natural chemical shielding ~NCS! analysis, an extension of natural bond orbital ~NBO! analysis. NCS analysis complements the description provided by ...