scholarly journals Quadrupole Coupling Assignments in Inorganic Periodic Systems by ab initio Calculation of Electric Field Gradients

1994 ◽  
Vol 49 (1-2) ◽  
pp. 137-145
Author(s):  
Michael H. Palmer ◽  
John A. Blair-Fish
Keyword(s):  
Electric Field ◽  
Ab Initio ◽  
Bulk Material ◽  
Basis Set ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Quadrupole Coupling ◽  
Periodic Behaviour ◽  
Coupling Parameters ◽  
Scf Calculations

Abstract Ab initio SCF calculations were performed in the unit cell environment, making use of the periodic behaviour to compute a wave-function for the bulk material. Electric field gradient (EFG) calcula­tions were performed on the resulting wave-functions, and these are compared with experimental quadrupole coupling parameters. Examples of inorganic molecular and ionic crystals (nitrogen, chlorine and lithium nitride) and minerals or partially covalent lattice structures (alumina, petalite, α-quartz, boron oxide, boron nitride and sulphur nitride) are described. The effects of the basis set in these calculations are considered, and the limitations imposed by the nature of the calculation are described.

Quadrupole Coupling in some H-bonded Organic Systems by ab initio Lattice Calculations of Electric Field Gradients

1994 ◽  
Vol 49 (1-2) ◽  
pp. 146-154
Author(s):  
Michael H. Palmer ◽  
John A. Blair-Fish
Keyword(s):  
Electric Field ◽  
Ab Initio ◽  
Bulk Material ◽  
Electric Field Gradients ◽  
Hartree Fock ◽  
Organic Systems ◽  
Field Gradients ◽  
Quadrupole Coupling ◽  
Lattice Calculations ◽  
Distant Neighbour

Abstract We present ab initio Hartree-Fock lattice calculations performed in the unit cell environment, to compute a wave-function and the derived electric field gradients for the bulk material. These calculations differ from cluster calculations by including the effects of more distant neighbour molecules. Examples considered are ammonia, formamide, oxamide, urea, thiourea, uracil, para-banic acid, alloxan, guanidine bicarbonate and melamine.

17O Nuclear Quadrupole Coupling in Molecular and Lattice Systems by ab initio Calculation of Electric Field Gradients

1996 ◽  
Vol 51 (5-6) ◽  
pp. 442-450
Author(s):  
Michael H. Palmer
Keyword(s):  
Electric Field ◽  
Ab Initio ◽  
Test Site ◽  
Coupling Constants ◽  
Basis Sets ◽  
Electric Field Gradients ◽  
Lattice Systems ◽  
Field Gradients ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Abstract We present ab initio Hartree-Fock calculations of electric field gradients, which are related to experimental determinations of nuclear quadrupole coupling constants. The nucleus of special interest is 17O but other nuclei in the molecules, especially 14N, 2H and 33S are included. The calculations were performed (a) as single molecules either at the SCF and MP2 correlated levels, (b) as clusters of molecules about a test site, or (c) as lattice calculations computed in the unit cell environment. The basis sets are triple zeta valence plus polarisation in (a). Because of limitations in exponent range in (c), the bases in both (b) and (c), where comparison was sought, are DZ at the SCF level.

Experimental and ab initio study of the electric field gradients at Ta and Cd impurities in TiAl3

2009 ◽  
Vol 479 (1-2) ◽  
pp. 56-59 ◽  
Author(s):  
P. Wodniecki ◽  
A. Kulińska ◽  
B. Wodniecka ◽  
J. Belošević-Čavor ◽  
V. Koteski
Keyword(s):  
Electric Field ◽  
Ab Initio ◽  
Ab Initio Study ◽  
Electric Field Gradients ◽  
Field Gradients

Molecular electric moments and electric field gradients from X-ray diffraction data: model studies

1996 ◽  
Vol 52 (6) ◽  
pp. 1023-1035 ◽  
Author(s):  
M. A. Spackman ◽  
P. G. Byrom
Keyword(s):  
Electric Field ◽  
Ab Initio ◽  
Diffraction Data ◽  
Moment Tensor ◽  
General Pattern ◽  
Valuable Insight ◽  
X Ray Diffraction ◽  
Electric Field Gradients ◽  
X Ray ◽  
Field Gradients

Model X-ray data sets, with and without the inclusion of experimental thermal motion parameters, have been computed via Fourier transformation of ab initio molecular electron densities for 12 different molecular crystals. These datasets were then analysed with three different multipole models of varying sophistication and, from the multipole functions, molecular dipole and second moments, as well as electric field gradients (EFG's), at each nuclear site were computed and compared with results obtained from the original ab initio wavefunctions. The results provide valuable insight into the reliability of these properties, extracted in the same way from experimental X-ray data. Not all molecular systems display identical trends, but a general pattern is discernible. Specifically, dipole moments are typically underestimated by a small but significant amount (~ 10–15%), the trace of the second moment tensor is well determined but overestimated by a few per cent and electric field gradients at protons are confirmed to be well within reach of a careful charge density analysis of X-ray diffraction data.

scholarly journals Electric field gradients in MgB2 synthesized at high pressure: 111Cd TDPAC study and ab initio calculation

2001 ◽  
Vol 119 (3) ◽  
pp. 153-158 ◽  
Author(s):  
A.V. Tsvyashchenko ◽  
L.N. Fomicheva ◽  
M.V. Magnitskaya ◽  
E.N. Shirani ◽  
V.B. Brudanin ◽  
...  
Keyword(s):  
High Pressure ◽  
Electric Field ◽  
Ab Initio ◽  
Ab Initio Calculation ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Tdpac Study

Ab initio studies of electric field gradients and magnetic properties of uranium dipnicties

RSC Advances ◽  
2015 ◽  
Vol 5 (47) ◽  
pp. 37592-37602 ◽  
Author(s):  
E. Ghasemikhah ◽  
S. Jalali Asadabadi ◽  
Iftikhar Ahmad ◽  
M. Yazdani-Kacoei
Keyword(s):  
Magnetic Properties ◽  
Electric Field ◽  
Ab Initio ◽  
Orbit Coupling ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Electric Field Gradients ◽  
Field Gradients

In this paper, we explore the electric field gradients (EFGs) at 238U sites for antiferromagnetic UX2 (X = P, As, Sb, Bi) dipnicties using LDA, LDA + U, GGA, GGA + U, and EECE schemes in the presence of spin–orbit coupling.

Electric Field Gradients Around Point Defects in Metals

1996 ◽  
Vol 51 (5-6) ◽  
pp. 489-505
Author(s):  
Alfred Seeger ◽  
Jörg Ehmann ◽  
Manfred Fähnle
Keyword(s):  
Electric Field ◽  
Ab Initio ◽  
Density Functional ◽  
Local Density ◽  
Energy Levels ◽  
Full Potential ◽  
Good Resolution ◽  
Quadrupole Moments ◽  
Electric Field Gradients ◽  
Field Gradients

The splittings of nuclear energy levels caused by the electric field gradients acting on the quadrupole moments of nuclei in the neighbourhood of atomic defects in cubic metals may serve as ‘‘fingerprints’’ providing us with a unique characterization of these defects. In favourable cases the NQDOR technique (n̲uclear q̲uadrupole d̲ouble r̲esonance) permits sensitive measurements of these splittings with good resolution. The present paper outlines the status of the ab-initio calculation of electric field gradients with emphasis on the theoretical basis (density functional theory with local density approximation) and on the techniques required for handling the specific problems associated with defects. Recent work by the supercell approach on atomic defects in Al and Cu, making use either of the full-potential linearized augmented-plane-wave method or of the ab-initio pseudopotential method, are reported and compared with experiments. The excellent agreement between experiment and theory for the field gradients acting on the nearest-neighbour nuclei of monovacancies in Al demonstrates the reliability and the potential of the theory.

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