In the form below: some fields allow input, some do not. Press RETURN to recalculate results. Values of read-only fields will be recalculated than. You might not be extra informed about the changes.

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This calculator gets an estimate of the chemical potential of the molecules (atoms in case of “½ H2” and “½ O2”) as required for so-called ab-initio thermodynamics or calculating adsorption/desorption equilibria in surface physics. It assumes an ideal gas, but it does not care whether the substance would exist as a gas under the given conditions. In case of doubt, use the Vapor Pressure Calculator to make sure.

For molecules not included in this calculator, the enthalpy H and entropy S per molecule can be calculated for a given temperature by the TPD Calculator (select “Calculation for: T_peak given”); the chemical potential is then given by μ = H − TS.

Data sources:
Based on M. W. Chase, NIST-JANAF Thermochemical Tables. Journal of Physical and Chemical Reference Data Monograph 9 (American Chemical Society & American Institute of Physics for the National Institute of Standards and Technology; Washington, D.C. & Woodbury, N.Y., 1998), using parametrization (Shomate Equation) from webbook.nist.gov, opens an external URL in a new window.
For the equations, see K. Reuter and M. Scheffler, Phys. Rev. B 65, 035406 (2001) [Erratum in Phys. Rev. B 75, 049901 (2007)].

Copyright © by Michael Schmid, IAP/TU Wien Surface Physics Group 2013–2024. No warranty for correctness of results.