First-principles study of clean tungsten surface work function under electric field

The effect of an external electric field on the work functions of clean tungsten (W) surfaces, W (100), W (110), and W (111) has been investigated using first-principles calculations based on density functional theory. By applying an electric field from 0 up to 0.3 V/Å, the effective and local work functions can be determined for comparison after employing five different pseudopotentials. It is found that as the electric field increases, the work functions of tungsten surfaces reduce accordingly. A reduction of work function can be as large as ∼0.35 eV. Based on these calculations, a new scaling law of work function reduction due to the charge transfer near the metal/vacuum interface caused by an external electric field is obtained. In addition, the local work function is found to be closely related to the charge density distribution. With this approach, field emission properties of metals can be better understood and described.