14N- and D-nuclear quadrupole coupling in the rotational spectrum of (CH3)314N…H(D)F: Modification of the electric field gradients at the N and D nuclei

1989 ◽  
Vol 157 (3) ◽  
pp. 243-250 ◽  
Author(s):  
A.C. Legon ◽  
C.A. Rego
Keyword(s):  
Electric Field ◽  
Rotational Spectrum ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

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.

scholarly journals Investigation of the Negative Thermal Expansion of ZrW2O8

2000 ◽  
Vol 55 (1-2) ◽  
pp. 301-310 ◽  
Author(s):  
N. Ulbrich ◽  
W. Tröger ◽  
T. Butz ◽  
P. Blaha
Keyword(s):  
Thermal Expansion ◽  
Electric Field ◽  
Negative Thermal Expansion ◽  
Temperature Structure ◽  
Full Potential ◽  
Electric Field Gradients ◽  
Quadrupole Interactions ◽  
Nuclear Quadrupole Interactions ◽  
Field Gradients ◽  
Nuclear Quadrupole

The negative thermal expansion in ZrW2O8 was investigated on a microscopic scale by temperature dependent measurements of the electric field gradients at the nuclear probe 187W(β-) 187Re using time differential perturbed angular correlation spectroscopy. Two distinct nuclear quadrupole interactions I VzzRe1 l= 18.92(4) • 10 21 V/m2 , ηRe1 = 0.0 and I VzzRe1 l = 4.55(2) • 1021 V/m2 , ηRe1 = 0.053(3) were observed at 295 K, which are assigned to the two crystallographically distinct W0 4 tetrahedra of the room temperature structure. Ab initio calculations of electron densities and electric field gradients with 1:7 Re-impurities using the full potential linearized augmented plane wave package WIEN97 yield the electric field gradients VzzRe1 = 12.63 • 10 21 V/m2 , ηRe1 = 0.0 and VzzRe2 =4.90 • 10 21 V/m2 , ηRe2 =0.0. The observed temperature dependence of the nuclear quadrupole interactions agrees well with the structural phase transition at 428 K observed by neutron and x-ray diffraction. Our experiments corroborate the suggested mechanism of coupled librations of rigid ZrO6 octahedra and WO4 tetrahedra, which is an alternative description of transverse vibrations of oxygen atoms in Zr-O-W bonds, for the negative thermal expansion in ZrW2 O8

Sign in / Sign up

Export Citation Format

Share Document