Thermal work function shifts for polycrystalline metal surfaces

A new approach is presented for the calculation of the thermal shifts of the work functions of polycrystalline metal surfaces by including the thermal expansion of the metal into the electron density parameter as well as Fermi energy. Calculations of dϕ/dT as a function of temperature are performed for 74 elements, encompassing a total of 103 cases of various temperature ranges, phases and (in a few cases) orientations. It is shown that for a majority of metals dϕ/dT is not a constant over a broad temperature range. Comparison of theoretical and experimental values indicates that the thermal lattice vibrations do not influence dϕ/dT significantly. Our results would suggest that the use of a Kelvin probe to measure the thermal variation of ϕ may be problematic.