Dear all,

I am trying to calculate Young's modules and Poisson's ratio of CNT and graphene sheet by using the Forcite modules. I used different atomic force fields , COMPASS, cvff and pcff  under both periodic and nonperiodic conditions however the poisson's ratio is about 0.46 which is more than twice of that in literature. The inter atomic bonds are SP2 and partially double bond.

Can anybody give me any idea about the source of problem?  Is that a problem with Material Studio and it's atomic force field or anything else?

Thanks in advance.