Optimal Electron Density Mechanism for Hydrogen on the Surface and at a Vacancy in Tungsten

In terms of first-principles investigation of H-tungsten (W) interaction,we reveal a generic optimal electron density mechanism for H on W(110) surface and at a vacancy in W.Both the surface and vacancy internal surface can provide a quantitative optimal electron density of~0.10electron/(A)3 for H binding to make H stability.We believe that such a mechanism is also applicable to other surfaces such as W( 100) surface because of the (100) surface also providing an optimal electron density for H binding,and further likely actions on other metals.