  The infuences of hydrogen on the generalized stacking fault (GSF) energies of
the basal plane along the <10-10> and <11-20> directions in the hcp Zr were
investigated using the first-principles calculation method. The modifications
of the GSF energies were studied with respect to the different distances of H
atoms away from the slip plane and hydrogen content there. The calculation
results have shown that the GSF energies along the < 10-10 > direction
drastically reduce when H atoms locate nearby the slip plane. But H atoms
slightly decrease the GSF barrier for the <11-20> slipping case. Meanwhile,
with the increase of hydrogen density around the slip plane, the GSF energies
along both the two shift directions further reduced greatly. The physical
origin of the reduction of GSF energies due to the existence of hydrogen atoms
in Zr was analyzed based on the Bader charge method. It is interpreted by the
Coulomb repulsion of the Zr atoms beside the slip plane due to the charge
transfer from Zr to H .
