[Pw_forum] about elastic constant

[Bipul Rakshit]

Dear PWSCF users,
In the paper of S Q Wang et al. J Phys. Cond. Matter 15 (2003) 5307,
(attached with this mail)
He uses three types of strains

1. Tri-axial shear strain to calculate C44
2. volume conservative orthorombic strain to calculate shear modulus C`
and
3. Hydrostatic pressure to calculate Bulk modulus.

In my calculations, on applying the 3rd strain, I am getting different
volumes for different set of strained lattice vectors (Volume non-conserve)
and 1st & 2nd type volume remain same (volume conserved)


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?

please guide me for the same.

-- 
Bipul Rakshit
PhD Student,
Barkatullah University,
Bhopal 462026,
MP, India
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