Dear Dr.Plimpton, users of LAMMPS

I received a valuable advice from the LAMMPS community on the use of PLUMED for free energy calculations.

However, i seek the following clarification. The use of pair potentials in MD are well known. Now, let us consider two elements, say U or Pu. Hypothetically, let us assume that the pair potentials are not known.

How can then we proceed further in finding the effective pair potentials for U-U, U-Pu and Pu-Pu.

I guess that this may not be the question to be submitted to LAMMPS mailing list, still I request the users to throw some light

on this as I would be using LAMMPS to calculate some thermodynamic properties of alloys.

Are their any methods within LAMMPS itself to find out effective potentials for systems when we do not have any experiemental information as to how they interact at high temperature when they are liquids.

Thank you

Suddhasattwa

Dear Dr.Plimpton, users of LAMMPS

I received a valuable advice from the LAMMPS community on the use of

PLUMED for free energy calculations.

However, i seek the following clarification. The use of pair

potentials in MD are well known. Now, let us consider two elements,

say U or Pu. Hypothetically, let us assume that the pair potentials

are not known.

then you have a big problem.

How can then we proceed further in finding the effective pair

potentials for U-U, U-Pu and Pu-Pu.

I guess that this may not be the question to be submitted to LAMMPS

mailing list, still I request the users to throw some light

on this as I would be using LAMMPS to calculate some thermodynamic

properties of alloys.

Are their any methods within LAMMPS itself to find out effective

potentials for systems when we do not have any experiemental

information as to how they interact at high temperature when they are

liquids.

what you want to do relates to the astounding stories of

baron munchhausen ( http://en.wikipedia.org/wiki/Baron_M�%

BCnchhausen )

in short, you cannot compute something from nothing.

you will have to research ways to generate some parameters

for the system that you are interested in. if you are

lacking experimental data, you may use (or generate) quantum

chemical data as an approximation. however, particularly for

elements as heavy as you indicate, those calculations are

far from trivial.

however, i suggest to have a closer look into the literature

to see, if there would be some potentials or at least some

studies of similar systems and suggestions for how to generate

suitable parameters.

cheers,

axel.