surfinpy: A Surface Phase Diagram Generator

Adam. R. Symington, Joshua Tse, Marco Molinari, Arnaud Marmier, Stephen C. Parker

Research output: Contribution to journalComment/debatepeer-review


A surface phase diagram is a graphical representation of the different physical states of a surface under different conditions. The surface represents the first point of contact between the material and the environment. Thus, understanding the state of surface is crucial for a wide range of problems in materials science concerning the relationship between the state of the surface and the surrounding environmental condtions. Examples include particle morphologies in solid state batteries (Canepa et al., 2018); determining the concentration of adsorbed water at a surface depending on synthesis conditions (Molinari, Parker, Sayle, & Islam, 2012) (Tegner, Molinari, Kerridge, Parker, & Kaltsoyannis, 2017); catalytic reactions (Reuter & Scheffler, 2003); or determing the effect of dopants and impurities on the surface stability.
Computational modelling can be used to generate surface phase diagrams from energy minimisation data. One common research question is how water adsorption affects the surface and material properties. The conventional starting point is to perform a series of energy minimisation calculations with varying concentrations of water on several different slabs. From the energies, the surface free energy of each calculation (phase) as a function of temperature and pressure can be calculated using a well-established approach (Molinari et al., 2012). Once the free energy is known under different constants, the phase which is most stable at a specific temperature and pressure, and thus a phase diagram, can be generated.
A further degree of complexity can be introduced by considering surface defects, e.g., vacancies or interstitials, or other adsorbants, e.g., carbon dioxide. Using surface defects as an example, it is important to consider the relationship between the defective surface, the stoichiometric surface and the adsorbing water molecules. A surface phase diagram can be constructed as a function of the chemcial potential of the adsorbing species (water) and the surface defect (e.g., oxygen, if oxygen vacancies are being considered). This is done using the method of Marmier & Parker (2004).
Original languageEnglish
Article number1210
Number of pages2
JournalThe Journal of Open Source Software
Issue number34
Publication statusPublished - 20 Feb 2019


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