Application of gradient-corrected density functional theory to the structures and thermochemistries of ScF3, TiF4, VF5, and CrF6

Abstract

Density functional theory(DFT) and Hartree-Fock(HF) calculations are reported for the family of transition metal fluorides ScF 3 , TiF 4 , VF 5 , and CrF 6 . Both HF and the local-density-aproximation (LDA) yield excellent agreement with experimental bond lengths, while the B-LYP gradient-corrected density functional gives bond lengths 0.04 − 0.05Å too long. An investigation of various combinations of exchange and correlation functionals shows that, for this series, the origin of this behavior lies in the Becke exchange functional. Much improved bond distances are found using the hybrid HF/DFT functional advocated by Becke. This approximation also leads to much improved thermochemistries. The LDA overestimates average bond energies in this series by 30 − 40 kcal/mol, whereas the B-LYP functional overbinds by only ∼ 8 − 12 kcal/mol, and the hybrid HF/DFT method overbinds by only ∼ 2 kcal/mol. The hybrid method predicts the octahedral isomer of CrF 6 to be more stable than the trigonal prismatic form by 14 kcal/mol. Comparison of theoretical vibrational frequencies with experiment supports the assignment of an octahedral geometry.

Surface model and exchange-correlation functional effects on the description of Pd/α-Al2O3(0001)

“…However, from quantum chemical applications it is known that for molecular systems the thermochemistry and energetics of a given chemical reaction are more accurately described using hybrid-type functionals. 30,[35][36][37] Notice that previous work has clearly shown that GGA has a marked tendency to overestimate the strength of the metal-oxide interaction. 18,19 This is the main reason for including hybrid functionals in the present systematic study.…”

“…It is important to note that the B3LYP hybrid functional has found wide applicability in molecular calculation and that in particular it is able to reproduce the thermochemistry of molecules containing transition metal atoms although no transition metal compounds were included in the data set used in its construction. [35][36][37] All adsorption energies calculated by means of cluster models have been corrected for possible basis set superposition errors using the standard counterpoise method.…”

Electronic and magnetic structure ofLaMnO3from hybrid periodic density-functional theory

“…It is worth pointing out that quite surprisingly, the B3LYP hybrid functional is able to reproduce the thermochemistry of molecules containing transition metal elements although no transition metal compounds were included in the data set used in the fit. [51][52][53][54] In a similar way, the Fock-35 and Fock-50 approaches combine a 35% or a 50% of Fock exchange with the Slater exchange and also use the standard Vosko-Wilk-Nusair correlation functional. For a more complete discussion about these hybrid approaches the reader is referred to Moreira et al 37 …”

Hydrolysis of Ferric Ion in Water and Conformational Equilibrium

“…Given the well known difficulties associated with electron correlation in transition metal complexes, and our intent to extend this work to larger and more complex systems, we chose to explore this problem with the B3LYP hybrid density functional theory (DFT) [12,13]. This approximation is an effective compromise between accuracy and computational expense, and has been shown to give usefully accurate predictions of metal-ligand bond energies in a number of molecules [14,15].…”