Potential Function for Tellurium Hexafluoride Molecules in the Solid

Abstract

How accurately various model intermolecular interaction functions are able to reproduce the detailed structure of orthorhombic TeF6 has been investigated by molecular packing analyses. Experimental structure parameters were extrapolated to the vibrationless limit. Model potential functions were six- and seven-site pairwise-additive atom−atom functions including partial charges. Lennard-Jones and Buckingham functions worked equally well. Scoles combining rules gave more consistent results than the conventional Lorenz−Berthelot and Good−Hope rules. Partial charges of approximately 0.21 e- on fluorine atoms gave the most accurate account of the experimental structure parameters. Potential functions based solely on interactions between fluorine sites were distinctly inferior to functions explicitly incorporating tellurium atoms. Although not required to do so by physical principles, the optimal partial charges for intermolecular interactions agreed well with charges derived for individual molecules by the Rappe−Goddard charge equilibration method.

Electronic Structure Predictions of the Energetic Properties of Tellurium Fluorides

“…The properties, especially the vibrational spectra, of TeF 6 have received significant attention. − The structure of TeF 6 has been obtained from a temperature dependent electron diffraction study and in the solid state by X-ray diffraction . TeF 6 has been studied computationally at the Hartree–Fock (HF), MP2 (second order Møller–Plesset perturbation theory), and density functional theory (DFT) (B88LYP, B3LYP, B88P86, and B3P86) levels. , Numerous papers have been published dealing with its electron affinity, force fields, , low energy electron attachment, potential function, first dissociative ionization energy, ionization potential, and F – affinity . The mass spectrum of TeF 6 was recently reported together with calculations on the ions at the B3LYP level with a large basis set …”

“…15 TeF 6 has been studied computationally at the Hartree−Fock (HF), MP2 (second order Møller−Plesset perturbation theory), and density functional theory (DFT) (B88LYP, B3LYP, B88P86, and B3P86) levels. 16,17 Numerous papers have been published dealing with its electron affinity, 18 force fields, 19,20 low energy electron attachment, 21 potential function, 22 first dissociative ionization energy, 23 ionization potential, 24 and F − affinity. 25 The mass spectrum of TeF 6 was recently reported together with calculations on the ions at the B3LYP level with a large basis set.…”

Molecular dynamics study of orientational order and rotational melting in clusters of TeF6

“…In all shells of all four monoclinic clusters studied the molecules in A sites had smaller rotational diffusion coefficients and rotational Lindemann indices, by perhaps 30%, than did those in B sites. On the other hand, there was little difference between molecules in the two sites with respect to their translational diffusion coefficients and Lindemann indices & Even though our primary criterion for rotational melting was based on the substantial increase in rotational freedom accompanying the transition to a disordered phase, our computations reveal a small but significant rotational diffusion in the ordered phase even at temperatures as low as 50 K. Although we are unaware of experimental measurements of molecular motions in monoclinic TeF 6, NMR studies of the orthorhombic phases of TeF 6 [32] and the very similar MoF 6 [33] (both of which have packing efficiencies nearly the same as those of the monoclinic phases [20]) show that the molecules continue to execute rotations well below the bccorthorhombic transition temperature.…”

“…Although the seeming anomalies are now well-understood [17][18][19], the system displayed properties that made it and its close relatives, SeF6, MoF6, and WF 6 particularly favorable subjects for MD investigations of structure and transformation. In a prior paper [19] in this series we investigated the relative stabilities of five distinct crystalline phases of TeF 6 (of the over one-dozen solid phases being analyzed currently [20]) and the size-dependence of melting points and other phase transitions of clusters. In the present work we sought to find whether crystalline clusters of the quasispherical molecule TeF 6 exhibit the phenomenon of rotational melting prior to translational melting.…”

Structural Aspects of Nanocrystals of Transition-Metal Hexafluorides

“… a Nanocrystal studies, this work; bulk, neutron diffraction. Charge on central atom in fractions of an electron (absolute magnitude of) from ref . b Reference 17. c Reference 3. d Reference 1. e Reference 6. f Reference 5. g Reference 2. …”