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Print virial components
#29006 12/29/11 02:57 AM
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hiva Offline OP
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Hello all,

I want to print the components if the internal and external virial, i.e. vixx viyy vizz and vexx veyy vezz.

First, what does internal and external rewfer to? Is it like bonded and non-bonded interactions?
Second, Is it possible to ask CHARMM to print out these properties during dynamics? If so, then how can I do that?

thanks,


Vahid Mirjalili
Mechanical Engineering
joint with Biochemistry
Re: Print virial components
hiva #29007 12/29/11 04:42 AM
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rmv Online Content
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The internal virial is more accurate, as it includes forces from all of the pairwise interactions; the external virial is more approximate, as it only considers interactions between primary and image atoms.

I believe it's possible to easily add these terms to the KUNIT file, if you don't mind changing the Fortran source code and re-compiling.


Rick Venable
computational chemist

Re: Print virial components
rmv #29016 01/04/12 10:10 PM
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The internal virial is the Sum(ij) of Fij*Rij.
It relates to the derivative of the energy with respect to homogeneous expansion of the unit cell.

The external virial represents the actual forces required to maintain the symmetry constraints. It relates to the derivative of the energy with respect to NON-homogeneous expansion of the unit cell.

As such the external virial depends on image centering, but the internal virial does not. Using the internal virial for determining pressure is the choice one must used when dealing with media that may diffuse.


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