[gmx-users] a bit strange errors

[Mark Abraham]

wuxiao wrote:
> Dear GMXers,
>    Recently, I has been performing coarse-grained MD simulations based 
> on the tabulated potentials using GROMACS. In the initialization, some 
> warnings are given as follows 
> /WARNING: For the 999 non-zero entries for table 0 in table_b0.xvg the 
> forces deviate on average 164% from minus the numerical derivative of 
> the potential/

This looks like your table has either wrong values or wrong formatting.
It does have to have equal spacing between entries.

> It proceeds untill at about 17 ns before it is interupted with some errors
> /WARNING: 1-4 interaction between 148 and 151 at distance 13.125 which 
> is larger than the 1-4 table size 2.000 nm/
> I think the duartion time is long enough to equilibrated the system, 
> which is confirmed by the energy plot with time. Why it happens so? What 
> should I do to cope with this problem? Thanks a lot for any reply to 

Perhaps much of the table is fine, and the problem only arises when you
get a force being looked up in an erroneous part.

Mark