Density Functional Calculations on WH₆ and WF₆

Abstract

We present the results of a computational study on both WH 6 and WF 6 using a relativistic pseudopotential on tungsten, comparing results at the HF and MP2 levels with density functional calculations using local (SVWN), nonlocal (BLYP), and hybrid HF-DFT (ACM) functionals. In agreement with the earlier all-electron HF study of Schaefer and co-workers ( J . Chem . Phys . 1993, 98, 508), we find that the ground state geometry of WH 6 is far from octahedral; instead, there are four low-lying structures of C 3 v (2) and C 5 v (2) symmetry. Barrier heights for interconversion of these isomers are low, indicating a highly fluxional molecule. In contrast, the octahedral structure appears to be the only stable species on the ground state potential energy surface of WF 6 . It derives its stability from the greater ionic character of the W−F bond compared to that of W−H.