The many-body expansion approach to ab initio calculation of electric field gradients in molecular crystals

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.

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

RSC Advances ◽

10.1039/c5ra02881g ◽

2015 ◽

Vol 5 (47) ◽

pp. 37592-37602 ◽

Cited By ~ 11

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.

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Electric Field Gradients Around Point Defects in Metals

Zeitschrift für Naturforschung A ◽

10.1515/zna-1996-5-624 ◽

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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The ab initio Calculation of Nuclear Quadrupole Coupling Constants and their Comparison with Experiment

Zeitschrift für Naturforschung A ◽

10.1515/zna-1990-3-425 ◽

1990 ◽

Vol 45 (3-4) ◽

pp. 357-367 ◽

Cited By ~ 2

Author(s):

Michael H. Palmer

Keyword(s):

Ab Initio ◽

Single Molecule ◽

Ab Initio Calculation ◽

Coupling Constants ◽

Structural Variations ◽

Electric Field Gradients ◽

Field Gradients ◽

Comparison With Experiment ◽

Quadrupole Coupling ◽

Nuclear Quadrupole

Abstract Ab initio calculations of electric field gradients (EFG) and conversion to nuclear quadrupole coupling constants (NQCC) are described, with particular reference to 14 N and 10,11B. The correlation of EFG and NQCC for a series of boranes leads to the value 8.32 MHz/a.u. (0.0354 barn) for Q(11B). The structural variations of these microwave and single molecule calculations of 10,11 B NQCC are discussed.

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