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[lammps-users] Poisson's effect during uniaxial strain in NVT
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[lammps-users] Poisson's effect during uniaxial strain in NVT


From: kia krn <kiakrn@...24...>
Date: Wed, 6 Dec 2017 16:01:40 +0900

Hello all
i am trying to perform uniaxial deformation simulations. if i use following:

fix         2 all deform 1 x erate  0.001 units box remap x
fix           relax all nvt temp 300.0 300.0 1.0
the strain is applied along x axis so only length along x axis changes and the length along y and z remain unchanged and exact volume change occur (i. e. 1% applied strain and 1% volume change occur) but here Poisson's effects is been neglected, which may be not physical application. according to LAMMPS documentation page fix deform if we can use volume style along the other sides but in such case volume remains constant and it documentation page says would may be not right unless Poisson's ratio for that materials is not 0.5.
 And documentation refers to "fix npt aniso" where we can make strain by applying pressure along one axis and keeping pressure along other sides zero. but in such case if i apply amount of pressure such that it produce desired i. e. 1% strain in one direction and consider passion's effect then in such case volume change will not be exact as the applied strain. so how we can consider poisson effect in NVT ensemble or produce more physical strain system with simulation. 

Thanks in advance.

Best regards,