Hello,
As a homework assignment I have my students approximate the C11, C12,
and C44 for NaCl using a Madelung sum. You can do the same using Siesta.
You begin by determining the ground state structure and energy. (There
are probably good examples of how to do this already.)
Next you can apply a series of strains. For a given strain you calculate
the change in the energy. (Make sure to use small strains.)
Then you use linear elasticity. (Note that this is in Einstein notation.)
sigma_ij = c_ijkl * epsilon_kl
Energy = 1/2 sigma_ij * epsilon_ij
Now you have Energy in terms of strains and coefficients c_ijkl. You
also have a set of strains, epsilon_ij, and corresponding energies.
You can then use software such as Mathematica, Octave, Matlab, etc... to
find the best fit for the coefficients c_ijkl.
Best,
Scott
On 10/16/12 11:50 AM, Michael Shin wrote:
Hi,
Can you explain me how to calculate C11, C12 and C44 for a BCC Fe.
Input files are welcome.
Please,explain me step by step.
Mic
--
Scott P. Beckman
Assistant Professor
Iowa State University
Department of Material Science and Engineering
Phone: 510-708-4390
http://zelda.engineering.iastate.edu/Beckman_Research/Home.html
