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How do I surface force constant from bulk force constants?
Posted: Tue Sep 05, 2006 2:18 am
by nfs21cn
From vasp I can get force constant matrix, but I need surface force constant.
How can I do that?
Plz help me
How do I surface force constant from bulk force constants?
Posted: Thu Sep 07, 2006 6:42 pm
by bandy
The size of force constant matrix(dynamical matrix) will depend on degrees of freedom calculated from POSCAR counting Ts at the right side. You can obtain force constant matrix from forces by writing a simple numerical finite difference code, or put write statement in vasp src and then recompile.
How do I surface force constant from bulk force constants?
Posted: Wed Sep 13, 2006 3:28 pm
by nfs21cn
Sorry, I can't understand "... Ts at the right side"
3x
How do I surface force constant from bulk force constants?
Posted: Wed Sep 13, 2006 4:31 pm
by bandy
nfs21cn wrote:
Code: Select all
Sorry, I can't understand "... Ts at the right side"
3x;
I do not understand what you mean by this. But once you
get forces for displacements of atoms, then you can get
force constants by finite difference method.
I hope that helps.
How do I surface force constant from bulk force constants?
Posted: Fri Sep 22, 2006 4:40 pm
by tjf
I think bandy is referring to the selective dynamics specifications. No selective dynamics gives 3.N