[QE-users] Bulk modulus - ev.x

[Inna Nangoi]

Hi,


I'm calculating the bulk modulus of different types of ice using ev.x.


>From the initial structure (.cif file) I increase and diminish the volume in around 7%. When the volume of .cif file is close to equilibrium volume, the calculation goes fine, with values of B0 and B0' close to experimental.


But when the volume of .cif file is far from equilibrium volume, more than 7% range , B0 goes too high and B0' is usually low (~1).


What is the right procedure to calculate the bulk modulus?

Should I vary volume until I find the lowest energy? Or should I always keep the range of around 7% from .cif file.


Thank you in advance,


Inna Nangoi
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