The SO-effect in transition metal hydrides

Anders Lund

Studenteropgave: Semesterprojekt

Abstrakt

The goal of this report is to estimate the Spin-Orbit effect on the ground state energies, bond lengths, ground state frequencies and formation energies for transition metal hydrides of the form $MH_2$, $MH_4$, $MH_6$ and $MH_{12}$ where M could be Cr, Mo an W. The geometries of the molecules have been optimized with a DFT and Spin-Orbit DFT procedure in the NWCHEM program package. The exchange functionals B3LYP, ACM and PBE0 have been used together with the CRENBL RECP uncontracted basis set for Cr, Mo and W and the 6-31G**,6-311++G(2d,2p) and 6-311++G(3df,3pd) basis set for H. The SO-effect shows a lowering of the ground state energy for Cr, Mo and W hydrides. For Cr hydrides it was estimated to be around 0.49 kcal/mol, for Mo hydrides to be around 2.5 kcal/mol and for W hydrides to be around 43 kcal/mol. There is not found any observable SO-effect on the bond length for Cr hydrides. For $MoH_4$ and $MoH_6$ there is seen a contraction of the bond length. For $MoH_{12}$ there is observed an elongation of the bond length. For W hydrides there is seen a contraction of the bond lengths for $WH$, $WH_2$, $WH_4$ and $WH_6$ from around $0.00080$ Å to $0.0018$ Å. The SO-effects on the frequency for Cr and Mo hydrides lies around $0.5-1.0 cm^{-1}$. For WH the SO-effect on the frequency is generally seen as a lowering of around $0.65-2.57 cm^{-1}$ and for $WH_2$ a lowering of the asymmetric streching frequency by around $2.14 cm^{-1}$ to $5.92 cm^{-1}$.

UddannelserKemi, (Bachelor/kandidatuddannelse) Kandidat
SprogEngelsk
Udgivelsesdato1 jan. 2005
VejledereJens Spanget-Larsen

Emneord

  • chemistry
  • Quantum