elastic constants
Posted: Fri Jun 20, 2014 12:47 am
Hey all,
I was trying to calculate the elastic constants of tungsten (C11,C12 and C44). I varied the size of the unit cell in one direction(a), thereby causing a strain of 1% on either side of the stable lattice constant (a0). I then calculated the elastic constant (c11) as
c11 = 2*(U - U0)/( V * e^2)
where U is the energy obtained by ab-initio calculations. U0 is the minimum energy corresponding to the minimum lattice constant, V is the volume corresponding to unit cell ( ao*ao*a) and e is the strain.
I expected a constant value over the range of variables , but i am getting quite a big scatter in the data. Is there something i am doing wrong?
Also is there any other direct way of calculating the elastic constants?
Thanks
I was trying to calculate the elastic constants of tungsten (C11,C12 and C44). I varied the size of the unit cell in one direction(a), thereby causing a strain of 1% on either side of the stable lattice constant (a0). I then calculated the elastic constant (c11) as
c11 = 2*(U - U0)/( V * e^2)
where U is the energy obtained by ab-initio calculations. U0 is the minimum energy corresponding to the minimum lattice constant, V is the volume corresponding to unit cell ( ao*ao*a) and e is the strain.
I expected a constant value over the range of variables , but i am getting quite a big scatter in the data. Is there something i am doing wrong?
Also is there any other direct way of calculating the elastic constants?
Thanks