Bulk moduli

Message

goja25 · #1 Post by **goja25** » Tue Sep 30, 2008 2:12 pm

Hi Dear
I want to calculate bulk moduli of PbTe. I have a question about that. What should I write in INCAR file?
Thank you
Margo

#2 Post by **admin** » Tue Sep 30, 2008 3:56 pm

the bulk modulus is best calculated from a fit of a set of E/V data
to Murnaghan's equation of state.

goja25 · #3 Post by **goja25** » Wed Oct 01, 2008 2:49 pm

Thanks for answer.
I will calculate the bulk modulus first time. I'm beginner, so I don't know this problem well. I have bulk of PbTe; first I relaxed this structure and obtained total energy and volume of this system. What should I do next?
Margo

forsdan · #4 Post by **forsdan** » Wed Oct 01, 2008 4:39 pm

1. I suggest you to start to do a series of isotropic expansions. This will provide you with values for the total energy as a function of volume.

2. Find you favorite equation of state, for example Murnaghan or Birch-Murnaghan equation of state:

http://en.wikipedia.org/wiki/Birch-Murn ... n_of_state

3. By fitting your data to the selected equation of state you will obtain the bulk modulus.

Otherwise there is always the possibility to calculate the bulk modulus from the elastic constants:
http://prola.aps.org/abstract/PRB/v41/i15/p10311_1

Cheers
/Dan