[gmx-users] Shift functions

Elisabeth katesedate at gmail.com
Fri Feb 10 15:19:17 CET 2012

> Hello all,
> Does the shift function use group based truncation?
> See the discussion of charge groups in manual section 3.4.2.

Thanks Mark.

-1- First of all if I am right  charge groups in gromacs language in
identical to "group based truncations"?

 Manual 342: "This reduces the cut-off effects from the charge-charge level
to the dipole-dipole level, which decay much faster"

2- I am not able to realize why we go from charge-charge the dipole-dipole

 In the manual I see: by using shifted forces there is no need for charge
> groups (=group based?!) in the neighbor list?
> Can anyone shed some light on calculation of shifted forces?
> What's not clear from the above and 4.1.5?

3- I understand that use of shift makes the potentials have continuous
derivatives at cutoffs but that how this makes use of charge groups
unnecessary, I dont see!

4- and based on 3,  shift forces dont neglect tail corrections for LJ as
cutoffs do? Am I correct?

Thank you
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