Influence of pressure on the valence bond structure of tungsten

The valence bond structure of tungsten is redetermined at ambient pressure and calculated for pressures up to 300 GPa using the energy and shape method. The outer shell valence electronic distribution of tungsten at ambient pressure is ec3.7408 (dc2.9268+Sc0.2040pc0.6100) ef2.2592. The value of the single-bond radius is 1.2532 Å. Under pressure, the covalent electrons ec (dc, sc and pc) increase while near free electrons ef decreases with increasing pressure. The number of covalent electrons ec is 3.7408 under ambient conditions and 5.0321 at 300 GPa and the number of near free electrons ef changes from 2.2592 at ambient pressure to 0.9679 at 300 GPa. The bond length and single-bond radius decrease while bond valence increases with increasing pressure. These results indicate that the electron distributions are more localized and the bonding character of metal becomes more covalent bonding with increasing pressure.