# TPD Calculator for a Lattice Gas

This page can simulate temperature programmed desorption (TPD) spectra. It can also calculate the adsorption energy distribution from an experimental TPD spectrum at saturation coverage.
For more information and the underlying theory, see M. Schmid, G. S. Parkinson, U. Diebold, Analysis of temperature-programmed desorption via equilibrium thermodynamics, ACS Phys. Chem. Au 2 (2022).
Currently this page does not include the “magic formula”, which determines the adsorption energy from the peak temperature and peak width. When the peak temperature is given, this calculator performs a TPD simulation based on the input data. You can then check whether the peak width agrees with experiment. If it doesn't, the assumptions made in the input (sticking coefficient, soft vibration modes, dissociation for molecules like H2, single adsorption energy vs. energy distribution, etc.) need to be questioned. When doing a simulation for a single adsorption energy, this page provides some thermodynamic data required for the magic formula (gray output below the input fields).

 Calculation for what E_ads given T_peak given Distribution of E_ads given TPD curve given, get E_ads distrib. Units J/mol eV Gas a)   dissociates Ramp rate β K/s Adsorption sites/area na m⁻² cm⁻² nm⁻² Tpeak K; FWHM = K |Eads0| J/mol   b) Adsorbate vibrations Evib cm-1   c) Extra entropy Sad,extra/R d) Initial coverage θ0 Multiple coverages e) Sticking:    Constant: s (mobile precursor) Per free site: s0 (Langmuir-type adsorption) Formula: s(θ, T) f)

Plot experimental TPD curve(s) for comparison

Legend

Export plot: T = K,    × pxl,  Line width pxl

T, Calculated desorption rate(s)

Author: Michael Schmid, IAP/TU Wien.