Electric field gradient tensors computation

The three components of the electric field gradient tensor are related by Poisson s equation, as shown earlier. However, the electrons that have a finite probability density at the nucleus, the s and p1/2 electrons, have a spherically symmetric distribution around the nucleus and as such do not contribute to E2. Thus, in the computation of E2, the Un can be related by... 

Computing Electric Field Gradient Tensors to Study Cl, and Quadrupolar Spins Recent advances in theory and computing power have made the computation of the electric field gradient (EFG) tensor parameters possible by first-principles methods and made quadrupolar spins a more valuable source of chemical information in solids. This section focuses on recent advances on the computational and experimental studies of APIs exploiting Cl, and quadrupolar nuclei. 

J.W. Zwanziger, Computing electric field gradient tensors, in R.E. Wasylishen, S.E. Ashbrook, S. Wimperis (Eds.), NMR of Quadrupolar Nuclei in Solid Materials, Wiley, Chichester, West Sussex, England, 2012, pp. 199-209. 

As described above for complexes of HCl with NH3 and PH3, Bacskay et al. have computed the vibrationally averaged component of the electric field gradient (EFG) tensor along... 

As will be made clear in the followings sections, accurate equilibrium stmcture as well as harmonic and anharmonic force field computations are necessary in order to fulfill point (a), dipole moment evaluations for point (b), and, finally, accurate electric field gradient, spin-rotation, and spin-spin tensor calculations for point (c). Additionally, vibrational corrections for properties related to points (a) to (c) are often required. 

Hyperfine Parameters From a quantum chemical point of view, the quantity required for the determination of the nuclear quadrupole-coupling tensor is the electric field gradient at the quadrupolar nucleus. This is a first-order property which can be computed as either the first derivative of the energy with respect to the nuclear quadrupole moment or the expectation value of the corresponding (one-electron) operator... 

Despite the importance of the nuclear quadrupole coupling in affecting the rotational spectra, the literature concerning the theoretical predictions of its related constants is rather limited. A significant example is provided by the recent investigation performed on the hyperfine structure in the rotational spectra of bromofluoromethane [75]. The experimental determination was supported by quantum chemical calculations of the nuclear quadrupole-coupling and spin-rotation tensors of Br and Br, performed at the CCSD(T) level in conjunction with core-valence correlation-consistent bases. Zero-point vibrational (ZPV) corrections were computed at the MP2 level in conjunction with the cc-pCVTZ basis set, whereas relativistic effects on the electric field gradient at the bromine... 

We have here introduced the static polarizability tensor elements (m,m ) these tensors are response properties of the molecule with respect to external electric fields F (with components F, eleclric field gradients VF (with elements VFcjp) and higher field derivatives, such as V F (with elements V Fcjp ), etc. It is possible to compute these quantities with the aid of PT techniques, but variational procedures are more powerful and more exact. 

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