Talk:Birch–Murnaghan equation of state
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I don't know, why the first cite was used - I found it on the PNAS server and did not find any link with what is titled Murnaghan equation. Apart from that, some hints should be made to account for the limits of these EOS (i.e. free energy, not internal energy,...)
I came across this 'Birch-Murnaghan' page when searching the web for the full expression of Birch-Murnaghan in E(V) form. I was happy to have found this page at first, but then noticed that the equation which you give there is the Murnaghan equation of state, not the Birch-Murnaghan. In my opinion, the title of this page should be changed to 'Murnaghan equation of state', and the occurrence of the word 'Birch' in the text should be deleted.
If anybody wants to include the correct Birch-Murnaghan expression, here it is:
introduce this notation: eta = (V0/V)**(1/3)
Then, E(V) is:
E(V) = E0 + 9/16*B*V0*[(eta**2-1)**3*BP + (eta**2-1)**2*(6-4*eta**2)]
And P(V) is:
P(V)=3/2*B*(eta**7 - eta**5)*(1 + 3/4*(BP-4)*[eta**2 - 1])
where B is the bulk modulus, BP its pressure derivative, V0 the equilibrium volume and E0 the equilibrium energy.
I have added these equations but it would be a good idea if sombody checks them! Andreww 11:14, 28 July 2005 (UTC)
