Electronic work function of the Cu (100) surface under different strain states

Surface electronic behavior of metallic materials induced by mechanical action or loading has been investigated experimentally, but the role of the deformation mode and further stress/strain state in such behavior has hardly been revealed theoretically. In this letter, we present a systematic study of the strain-dependent work function (WF) on the Cu (100) surface using first-principles calculations. We employ four deformation modes, namely, uniaxial, biaxial and triaxial as well as perpendicular, to demonstrate the strong dependence of the WF on strain states. We find that the compressive state makes the WF increase but the tensile state makes the WF decrease, whereas the lateral strain state can affect strongly the WF but the perpendicular state can hardly do so. Furthermore, both the bi- and triaxial strain states lead to a larger WF change than other two states. The mechanism responsible for the above changes in WF can be related to the effects of strain states on the bulk cell volume and redistributed charge density and the resultant bulk electronic structures and surface dipoles.