First principles study of nuclear quadrupole interactions in the molecular solid BF3 and the nature of binding between the molecules

Abstract

The electronic structures and nuclear quadrupole interactions (NQI) of the 19 F* (I = 5/2) state of 19 F nucleus in solid BF 3 are studied using the first-principles Hartree-Fock-Roothaan procedure including many-body electron correlation effects. The calculated NQI parameters, 19 F* quadrupole coupling constant (e 2 qQ) and asymmetry parameter η, were found to be in satisfactory agreement with experiment for the solid state system, which gives confidence in the reliability of the calculated electronic structures in the solid and hence the factors found to influence the binding of the molecules in the solid. It was found that the intermolecular binding energy primarily arises from Van der Waals (VDW) interactions between the molecules resulting from intermolecular many-body effects, which counteract the repulsive interactions between the molecules arising from one-electron Hartree-Fock (HF) theory.

Nuclear quadrupole interactions and electronic structure of BF3 ∙H2O complex

“…In the present work, as in our other recent investigations on BF 3 systems [2,3], we have used first principles variational Hartree-Fock-Roothaan procedure [4] combined with Many Body Perturbation Theory [5] for inclusion of electron correlation effects to investigate both the binding or dissociation energy of the complex and the 19 F* NQI parameters [6]. The latter are not currently available but can be measured by the Time Dependent Perturbed Angular Distribution (TDPAD) technique which has already been applied [7] to the BF 3 •NH 3 complex and BF 3 in solid state.…”

“…Since our results for BF 3 -NH 3 system, where convergence with respect to the size of variational basis sets for the dissociation energy and NQI parameters have been tested carefully and shown that the results for (6-311G) basis set including (3df, 3pd) polarization functions [8] are most reliable, we have chosen this basis set for our investigations on BF 3 …”

“…271, 273 (1993), which is 30% higher than the value[8] used in this paper, and leads to correspondingly higher e 2 qQ than those listed inTable 3. However the suggestion by the authors of the later value of Q( 19 F*) that many-body effects are responsible for their substantially larger result needs to be further tested, which is in progress in our group using the molecule FCl employed in[8], as well as the study of the influence of solid state effects[3] in the FCl molecular solid.…”

Theory of electronic structure and nuclear quadrupole interactions in the BF3–NH3 complex and methyl derivatives

“…The experimental results for the 19 F* NQI parameters are of course for the solid state systems while our calculated results are for the free molecules of BF 3 and the four complexes. But as we have shown in the paper from our group [8] on solid BF 3 , there are only small differences between e 2 qQ/ h and η for the free molecule and solid BF 3 . One therefore expects similar small differences in the case of the free complexes and corresponding solid state systems.…”

“…Finally we calculate the NQI parameters at the excited 19 F* nucleus in the free BF 3 molecule and the four BF 3 ·NH x (CH 3 ) 3−x (x = 0,1,2,3) complexes. The electric field gradient tensor [8] (EFG) is obtained from our calculated wavefunctions and diagonalized to obtain the principal axis components, V xx , V yy , and V zz , where convention dictates that |V zz | > |V yy | > |V xx |. The EFG tensor is then represented by two parameters, the largest component q = V zz which is used to obtain the nuclear quadrupole coupling constant e 2 qQ/ h, and the asymmetry parameter η = (V xx − V yy )/V zz .…”