Advanced

Nuclear quadrupole interactions in cadmium complexes : Semiempirical and ab initio calculations

Hemmingsen, Lars; Ryde, Ulf LU and Bauer, Rogert (1999) In Zeitschrift fur Naturforschung - Section A Journal of Physical Sciences 54(6-7). p.422-430
Abstract

Semiempirical calculations, based on the so-called angular overlap model, have been compared with ab initio methods (MP2) for the calculation of nuclear quadrupole interactions (NQI's) in cadmium complexes with biologically relevant ligands (H2O, OH-, cysteinate, carboxylate, and imidazole). The assumptions on which the semiempirical model is based have been tested and the comparison indicates that: 1) A change in the Cd-ligand bond length by 0.1 Å may change the electric field gradient (EFG) by about 0.2 a. u.. A simple scheme to incorporate such effects in the semiempirical method is suggested. 2) The effect of ligand-ligand interactions is up to about 0.2 a. u. for the largest diagonal element of the EFG tensor... (More)

Semiempirical calculations, based on the so-called angular overlap model, have been compared with ab initio methods (MP2) for the calculation of nuclear quadrupole interactions (NQI's) in cadmium complexes with biologically relevant ligands (H2O, OH-, cysteinate, carboxylate, and imidazole). The assumptions on which the semiempirical model is based have been tested and the comparison indicates that: 1) A change in the Cd-ligand bond length by 0.1 Å may change the electric field gradient (EFG) by about 0.2 a. u.. A simple scheme to incorporate such effects in the semiempirical method is suggested. 2) The effect of ligand-ligand interactions is up to about 0.2 a. u. for the largest diagonal element of the EFG tensor for the tested complexes, and such effects can significantly influence the so-called asymmetry parameter. 3) The position of non-coordinating atoms on the ligands can in some cases (e. g. the hydrogen atoms of water) significantly influence the EFG. The combined effect of non-coordinating atoms and ligand-ligand interactions may cause deviations of up to 0.35 a. u. between ab initio and the semiempirical calculations. 4) In the semiempirical model each ligand is characterised by one parameter, the so-called partial nuclear quadrupole interaction. This parameter has been evaluated by ab initio calculations, and agreement was found within about 0.2 a. u. (≈ 40 Mrad/s) for all ligands except imidazole. 5) A change in the coordination number from 2 to 6 may change the partial NQI by about 0.3 a. u.

(Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Angular Overlap Model, Electric Field Gradient, Ligand Additivity
in
Zeitschrift fur Naturforschung - Section A Journal of Physical Sciences
volume
54
issue
6-7
pages
9 pages
publisher
De Gruyter
external identifiers
  • scopus:0040122450
ISSN
0932-0784
DOI
https://doi.org/10.1515/zna-1999-6-713
language
English
LU publication?
yes
id
e4cb55e4-6a02-4a62-83d2-5fe0db351678
date added to LUP
2017-02-04 11:41:03
date last changed
2017-08-13 05:03:55
@article{e4cb55e4-6a02-4a62-83d2-5fe0db351678,
  abstract     = {<p>Semiempirical calculations, based on the so-called angular overlap model, have been compared with ab initio methods (MP2) for the calculation of nuclear quadrupole interactions (NQI's) in cadmium complexes with biologically relevant ligands (H<sub>2</sub>O, OH<sup>-</sup>, cysteinate, carboxylate, and imidazole). The assumptions on which the semiempirical model is based have been tested and the comparison indicates that: 1) A change in the Cd-ligand bond length by 0.1 Å may change the electric field gradient (EFG) by about 0.2 a. u.. A simple scheme to incorporate such effects in the semiempirical method is suggested. 2) The effect of ligand-ligand interactions is up to about 0.2 a. u. for the largest diagonal element of the EFG tensor for the tested complexes, and such effects can significantly influence the so-called asymmetry parameter. 3) The position of non-coordinating atoms on the ligands can in some cases (e. g. the hydrogen atoms of water) significantly influence the EFG. The combined effect of non-coordinating atoms and ligand-ligand interactions may cause deviations of up to 0.35 a. u. between ab initio and the semiempirical calculations. 4) In the semiempirical model each ligand is characterised by one parameter, the so-called partial nuclear quadrupole interaction. This parameter has been evaluated by ab initio calculations, and agreement was found within about 0.2 a. u. (≈ 40 Mrad/s) for all ligands except imidazole. 5) A change in the coordination number from 2 to 6 may change the partial NQI by about 0.3 a. u.</p>},
  author       = {Hemmingsen, Lars and Ryde, Ulf and Bauer, Rogert},
  issn         = {0932-0784},
  keyword      = {Angular Overlap Model,Electric Field Gradient,Ligand Additivity},
  language     = {eng},
  number       = {6-7},
  pages        = {422--430},
  publisher    = {De Gruyter},
  series       = {Zeitschrift fur Naturforschung - Section A Journal of Physical Sciences},
  title        = {Nuclear quadrupole interactions in cadmium complexes : Semiempirical and ab initio calculations},
  url          = {http://dx.doi.org/https://doi.org/10.1515/zna-1999-6-713},
  volume       = {54},
  year         = {1999},
}