GrueneisenCoefficient - output Cv(T)?

[Joao Amaral]

The recent addition of GrueneisenCoefficient in W.2024.9 is very welcome. Both the Grueneisen coefficient and linear thermal expansion coefficient with their temperature dependence are direct outputs. It seems Cv (temperature-dependent heat capacity at constant volume) is internally calculated to allow the estimate of these two parameters. Can Cv also be an output of the GrueneisenCoefficient class?

[Anders Blom]

Yes, there is a hidden query function _modeHeatCapacities on the GrueneisenCoefficient study object class which returns Cv(q,i,T) if you provide it with a temperature. I suppose you just sum over the modes and qs to get the total. You might need to normalize by volume by dividing by the total number of repetitions used in the DynamicalMatrix, at least that is what we do after multiplying gamma and Cv to get the linear thermal expansion coefficient (https://docs.quantumatk.com/manual/Types/GrueneisenCoefficient/GrueneisenCoefficient.html).

[Joao Amaral]

Excellent, thanks for the information! Building on the provided example of Si, I reached these results: Hill bulk modulus (~99.4 GPa) and room temperature Cv (~4.4E5 J K-1 m-3).