[Pw_forum] Compute bulk modulus by using the formulae of P-V and E-V Birch–Murnaghan equation of state.
Paolo Giannozzi
giannozz at democritos.it
Wed Jul 30 19:24:00 CEST 2008
On Jul 12, 2008, at 17:09 , zhaohscas wrote:
> I've read from the different literatures that there are two forms
> of the P-V Birch–Murnaghan equation of state:
>
> a) P(V) = \frac{{3B_0 }}{2}\left[ {\left( {\frac{{V_0 }}{V}}
> \right)^{\frac{7}{3}} - \left( {\frac{{V_0 }}{V}} \right)^{\frac{5}
> {3}} } \right]\left\{ {1 + \frac{3}{4}\left( {B_0^' - 4} \right)
> \left[ {\left( {\frac{{V_0 }}{V}} \right)^{\frac{2}{3}} - 1}
> \right]} \right\}
>
> b) P(V) = \frac{{3B_0 }}{2}\left[ {\left( {\frac{{V_0 }}{V}}
> \right)^{\frac{7}{3}} - \left( {\frac{{V_0 }}{V}} \right)^{\frac{5}
> {3}} } \right]\left\{ {1 + \frac{3}{4}\left( {4 - B_0^'} \right)
> \left[ {\left( {\frac{{V_0 }}{V}} \right)^{\frac{2}{3}} - 1}
> \right]} \right\}
>
> Where, the B_0 and the B_0^' are the bulk modulus and its pressure
> derivative respectively. Which of the above is correct?
the one that is obtained by derivation of the Birch-Murnaghan
equation of state
E(V). I cast my vote for a), since this is what I used once upon a
time in a routine
that calculates P(V)
Paolo
---
Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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