Hi Sunetra, There are a number of other equations of state you can use. See for instance:
https://doi.org/10.1016/j.cpc.2011.04.016 and references therein. You can do the fit with a instead of V if you want, but then note that you'll have to use the chain rule to write E''(V) in terms of E'(a) and E''(a), and the expression will depend on the V(a) function. You also need to make sure that E and V, which are extensive quantities, correspond to the same number of atoms. Otherwise, you'll be an integer factor off the correct result. Best, Alberto --- Dr. Alberto Otero de la Roza Department of Chemistry, University of British Columbia, Okanagan Kelowna, British Columbia, Canada V1V 1V7 * Sunetra Das <[email protected]> [2017-08-16 22:06:01 +0530]: > Dear QE users, > > I would like to know if there are any other equation of state that we can > use to fit the 'etot vs alat' graph to find out the equilibrium lattice > constant. I have been following the QE tutorials to learn the basics where > it has been demonstrated how to fit a etot vs alat graph using the four > given equations of state. But none of the obtained equilibrium bulk modulus > values from those equation fitting match the given experimental value, not > even close. > How to improve the fitting of the equations or is there any other equation > I can use to fit the obtained data? > > I am new to QE, any suggestion is highly appreciated. > > Thank you. > > Regards, > Sunetra Das > Assistant Professor, > MMC College, Kolkata, WB, > India. > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
