PME and cutoffs - 08/25/13 05:12 AM

I wonder what are recommended cutoff parameters for non-bonded interactions (in particular VDW) when using PME.

In nbonds.doc I read:

For no-cutoff periodic systems:

NBONDS ATOM EWALD PMEWALD KAPPA 0.32 -

FFTX 32 FFTY 32 FFTZ 32 ORDER 6 -

CUTNB 12.0 CTOFNB 10.0 VDW VSHIFT

So, here the recommendation is 9/10/12 for CTONNB/CTOFNB/CUTNB

However, in file c26test/pme_p21.inp I find:

dyna verlet ... -

cutnb 12.0 ctofnb 10. cdie eps 1. -

ctonnb 9.99 vshift cutim 14.0 imgfrq 25 wmin .5 -

ewald pmewald

So, here they have 9.99/10/12 which corresponds to an almost abrupt truncation of VDW.

I would appreciate any advice on this. Thanks!

In nbonds.doc I read:

For no-cutoff periodic systems:

NBONDS ATOM EWALD PMEWALD KAPPA 0.32 -

FFTX 32 FFTY 32 FFTZ 32 ORDER 6 -

CUTNB 12.0 CTOFNB 10.0 VDW VSHIFT

So, here the recommendation is 9/10/12 for CTONNB/CTOFNB/CUTNB

However, in file c26test/pme_p21.inp I find:

dyna verlet ... -

cutnb 12.0 ctofnb 10. cdie eps 1. -

ctonnb 9.99 vshift cutim 14.0 imgfrq 25 wmin .5 -

ewald pmewald

So, here they have 9.99/10/12 which corresponds to an almost abrupt truncation of VDW.

I would appreciate any advice on this. Thanks!