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

Abstract

Magnetic Hyperfine and Nuclear Quadrupole Interactions (HFI and NQI) are now important tools for characterization of systems of interest in materials research and industry. Boron-Trifluoride is an inorganic compound that is very important in this respect as a catalyst in chemical physics research and industry, forming complexes in the process with compounds like ammonia, water and methyl alcohol. The present paper deals with the BF 3 -NH 3 complex and methyl derivatives BF 3 NH x (CH 3 ) 3−x for which we have studied the electronic structures, binding energies, and 19 F* (I = 5/2) nuclear quadrupole interactions using the first-principles Hartree-Fock-Roothaan procedure combined with electron correlation effects. Our

Nuclear quadrupole interactions and electronic structure of BF3 ∙H2O complex

“…Thus, the VDW contribution is about 56% of the total dissociation energy as compared to 44% from the one-electron, or covalent, contribution. This result is in contrast to the corresponding result [2] in BF 3 -NH 3 , where the VDW contribution is only about 27% of the dissociation energy with the covalent contribution making the dominant contribution of 73%. The result of the relatively larger VDW contribution as compared to the covalency Table 3 the values of e 2 qQ/h and η for BF 3 •H 2 O and BF 3 molecules that we have obtained both from Hartree-Fock investigation alone for the electronic structure, and when combined with many-body effects.…”

“…The BF bond distances with these atoms are non-planar and B atom is significantly below its symmetric position on the BF 3 plane in pure BF 3 . Our optimized bond parameters show that the BF bond distances in BF 3 •H 2 O complex are slightly larger than that (0.134 nm) in the free BF 3 molecule, a trend similar to that observed [2] in BF 3 •NH 3 complex.…”

“…There is again a substantial decrease in η as in the case of the BF 3 •NH 3 complex in going from BF 3 to the BF 3 •H 2 O complex, reflecting the change in the axial symmetry of the electron distributions around the F atoms due to the complexation process. The average value of e 2 qQ/h for 19 F* from the fourth column of Table 3, of about 26.50 MHz, is reasonably close to the value [2] of 25.33 MHz for BF 3 •NH 3 , which is not unexpected because the effective charges on the F-atoms are quite close in the two complexes. The value 0.171 of η for BF 3 •H 2 O is somewhat higher than the calculated value of 0.137 for BF 3 •NH 3 .…”

“…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.…”

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

“…For the evaluation of the dissociation energy of each BF 3 molecule in the cluster simulating the solid, we have adopted the procedure described in the cases of the molecular complexes [7,8] BF 3 -NH 3 , BF 3 -H 2 O and solid halogens [1]. We have used the pair approximation as in these other systems, calculating, and summing, the pair dissociation energies for the central molecule with each of the four nearest neighbors using HF procedure combined with MBPT.…”