[Pw_forum] about elastic constant

[Michael Mehl]

Bipul Rakshit wrote:

> Because in order to calculate 3 elastic constants (C11, C12 and C44) we 
> require 3 equations, so do I have to use the above three equations, both 
> type (volume conservative and non-conservative) to calculate a single 
> set of elastic constants?

Yes.

> 
> please guide me for the same.

You'll have to compute the bulk modulus at same volume that you use to 
compute C44 and C11-C12.  In a cubic system B = (C11+2 C12)/3, giving 
you enough information to get all three elastic constants at that volume.

There are many, many programs that will compute B(V), see this list's 
archives for details.

My favorite reviews of the subject are:

http://cst-www.nrl.navy.mil/users/mehl/papers/cij453.pdf

and

Phys. Rev. B 47, 2493 (1993)

but I may be somewhat biased.

-- 
Michael J. Mehl, Naval Research Laboratory, Washington DC
On Sabbatical at Duke University until 31 July 2009