respa

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1

I am simulating a system consisting of 128 phosphonium ions consisting of one central charged phosphorous atom with four alkyle ligand and 128 negative borate ions. When I simulate this system at constant pressure using run_style respa with the recommended parameters in the manual

run_style respa 4 2 2 2 inner 2 4.5 6.0 middle 3 8.0 10.0 outer 4

the system contracts to an unphysically high density. If I use this alternative:

run_style respa 2 2 bond 1 angle 1 dihedral 1 improper 1 pair 1 kspace 2

I get the correct density or at least a density that agrees with the one obtained from other programs but only if the timestep is very short - 0.4 fs. Therefore I would be very grateful if someone could tell whether ther is a better choice of paramaters for run_style respa.

Thank you im advance for the answer

Sten Sarman

2

I am simulating a system consisting of 128 phosphonium ions consisting of
one central charged phosphorous atom with four alkyle ligand and 128
negative borate ions. When I simulate this system at constant pressure using
run_style respa with the recommended parameters in the manual

run_style respa 4 2 2 2 inner 2 4.5 6.0 middle 3 8.0 10.0 outer 4

the system contracts to an unphysically high density. If I use this
alternative:

run_style respa 2 2 bond 1 angle 1 dihedral 1 improper 1 pair 1 kspace 2

I get the correct density or at least a density that agrees with the one
obtained from other programs but only if the timestep is very short - 0.4
fs. Therefore I would be very grateful if someone could tell whether ther is
a better choice of paramaters for run_style respa.

Thank you im advance for the answer

before going that way. can you run this system well with run_style verlet?

and at what time step?

there are tons of things that could be wrong.

axel.