Calculation of isosteric heats of molecular gas and vapor adsorption on graphite using density functional theory

Isosteric heats of hydrogen, nitrogen, and methane adsorption on graphite surface have been calculated and analyzed using the density functional theory. The heats of adsorption have been calculated within wide ranges of pressures and subcritical temperatures. The peaks in the temperature dependences of isosteric heat of adsorption have been found to correlate with the degrees of filling of monolayers during adsorption.