scholarly journals Density functional calculations of nuclear quadrupole coupling constants in the zero-order regular approximation for relativistic effects

2000 ◽  
Vol 112 (19) ◽  
pp. 8279-8292 ◽  
Author(s):  
Erik van Lenthe ◽  
Evert Jan Baerends
Keyword(s):  
Density Functional Calculations ◽  
Density Functional ◽  
Relativistic Effects ◽  
Zero Order ◽  
Coupling Constants ◽  
Regular Approximation ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Density Functional Theory Studies of Bonding in Complexes H3N···XY of Ammonia and Dihalogen Molecules: A Comparison with Experimental Results from Rotational Spectroscopy

2002 ◽  
Vol 57 (6-7) ◽  
pp. 537-543 ◽  
Author(s):  
O. Kh. Poleshchuk ◽  
A. C. Legona
Keyword(s):  
Density Functional ◽  
Natural Bond Orbital ◽  
Coupling Constants ◽  
Rotational Spectroscopy ◽  
Charge Redistribution ◽  
Functional Theory ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Experimental Values

The electron density and nuclear quadrupole coupling constants (NQCC) of the H3N...XY (n a type in Mulliken notation) complexes, (X, Y = F, Cl, Br and I), are analyzed with the aid of density functional calculations. To demonstrate the quality of the calculations, various bond lengths and NQCCs obtained by using the hybrid Becke-Lee-Perdew-Yang functional are compared with the corresponding experimental values determined from rotational spectroscopy. An analysis of the NQCC values and various quantities derived fromthe natural bond orbital approach reveals that the molecular interaction is mainly electrostatic, with probably only a small extent of intermolecular electric charge redistribution on complex formation

COMPUTATIONAL STUDY OF A CNT-URACIL-CNT COMPOUND

2011 ◽  
Vol 25 (15) ◽  
pp. 1335-1341 ◽  
Author(s):  
MARYAM MIRZAEI ◽  
MOHAMMAD YOUSEFI ◽  
MAHMOUD MIRZAEI
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Computational Study ◽  
Dipole Moments ◽  
Coupling Constants ◽  
Modification Process ◽  
Quadrupole Coupling ◽  
Electronic Environments ◽  
Oxygen Atoms

Density functional calculations were performed to investigate the properties of a combination of two representative carbon nanotubes by assistance of the atomic sites of uracil, which is the characteristic nucleobase of RNA. The obtained parameters indicated that the resulting compound exhibit new properties with respect to the original nanotubes and uracil. The effects of the modification process were significant for the dipole moments and conductivity properties of the components as were seen by the significant changes in the new compound. The values of quadrupole coupling constants for the nitrogen and oxygen atoms of the uracil counterpart of the investigated models also indicated the effects of changes of the electronic environments of the components due to the modification process.

Halogen Nuclear Quadrupole Coupling Constants in Non-axially symmetric Molecules; Ab initio Calculations, which Include Correlation, Compared with Experiment

1998 ◽  
Vol 53 (6-7) ◽  
pp. 370-382
Author(s):  
Michael H. Palmer ◽  
John A. Blair-Fish
Keyword(s):  
Ab Initio ◽  
Relativistic Effects ◽  
Close Correlation ◽  
Equilibrium Structure ◽  
Cylindrical Symmetry ◽  
Coupling Constants ◽  
Axially Symmetric ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Abstract Ab initio determination of the electric field gradient (EFG) tensors at halogen and other centres ena-bled determination of the nuclear quadrupole coupling constants (NQCC) for a diverse set of C2v , C3v and other symmetry molecules of general formula MH2X2 and MHX3 , where the halogen atoms (X) are Cl, Br and I, and the heavy central atoms (M) are C and Si. The study presents results at a standardised level of calculation, triple-zeta in the valence space plus polarisation functions (TZVP) for the equilib-rium geometry stage; all-electron MP2 correlation is included in all these studies. For the bromo and iodo compounds, especially the latter, it is essential to allow core polarisation, by decontraction of the p,d-functions. This is conveniently done by initial optimization of the structure with a partly contract-ed basis, followed by reestablishment of the equilibrium structure with the decontracted basis.The NQCCs, derived from the EFGs, using the 'best' values for the atomic quadruple moments Cl, Br and I, lead to good agreement with the inertial axis (IA) data obtained from microwave spectroscopy. When the data from the present study is plotted against the values derived from the IA data, obtained by whatever approximations chosen by the MW authors, we obtain a linear regression for the data (85 points) with the slope 1.0365 and intercept -0.1737, with standard errors of 0.0042 and 0.2042, respectively; these are statistically identical results irrespective of whether the data is restricted to IA or EFG principal axis (PA) data.Since as in the C3v MH3X compounds studied previously, a close correlation of the microwave spectral data with the calculations was observed using the 'best' current values for Qz , there seems no need to postulate that the values of QBr for both 79Br and 81Br are seriously in error. A scaling downwards of Qz by about 5% for Br and I increases the agreement with experiment, but the contributions of relativistic effects are unknown, and could lead to further reassessment.Of the two common assumptions used in MW spectroscopy, to convert from IA to EFG-PA data, either (a) cylindrical symmetry of the NQCC along the bond direction, or (b) coincidence of the tensor principal element with the bond axis, the latter is found to be a much more realistic approximation.

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