Shifted Potential vs Shifted Force of LJ

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1

Dear All,

Want to clarify some fundamental concepts of the shifted potential and shifted force model:

shifted potential:

pair_style lj/cut 2.5

pair_modify shift yes

shifted force:

pair_style lj/sf 2.5

2.5 is the conventional cut-off value. For a specific application, I have to decided which value to use,
but what is the criteria for a 'good ’ value?

Also, does shifted force always superior to shifted potential with the same cutoff?

Those two corrections just modified the energy and didn’t change the dynamics?

For those two corrections, when we do the post-process, should we include the shifted effect?
for example, when calculating the total energy and pressure etc?

Thanks in advance for your reply!

Best Wishes!

2

Dear All,

Want to clarify some fundamental concepts of the shifted potential and shifted force model:

shifted potential:

pair_style lj/cut 2.5
pair_modify shift yes

shifted force:

pair_style lj/sf 2.5

2.5 is the conventional cut-off value. For a specific application, I have to decided which value to use,
but what is the criteria for a 'good ’ value?

Error from cutoff is small enough. 2.5x sigma is pretty much the lower limit.

Also, does shifted force always superior to shifted potential with the same cutoff?

Depends.

Those two corrections just modified the energy and didn’t change the dynamics?

No.

For those two corrections, when we do the post-process, should we include the shifted effect?
for example, when calculating the total energy and pressure etc?

Depends. Usually not.

3

For details of the difference between the 2 models,
you should read the doc pages. It gives the eqs
and what is meant (in LAMMPS) by shift.

Steve