AMBER Archive (2005)

Subject: Re: RE: AMBER: problem with gb md

From: Andreas Svrcek-Seiler (svrci_at_tbi.univie.ac.at)
Date: Fri May 06 2005 - 04:19:00 CDT


Hi,
> Thank for your suggestions. i checked my initial structure in xleap,and the result is that the unit is ok. when i used igb=2 instead of igb=1, everything is fine, so i think the structure is reasonable.
>

>
> ======= 2005-05-06 12:47:40 您在来信中写道:=======
>
>> Dear Emilia,
>>
>>> NSTEP ENERGY RMS GMAX
>>> NAME NUMBER
>>> 1 nan nan 0.0000E+00
>>> C34 1
>>>
>>> BOND = 199.1390 ANGLE = 606.5759 DIHED
>>> = 2318.4901
>>> VDWAALS = 134604.7930 EEL = -18304.6508 EGB
>>> = nan
>>> 1-4 VDW = 1344.4585 1-4 EEL = 11078.6900 RESTRAINT
>>> = 0.0000
>>> ==============================================================
>>> ============
...1)EEL is large, but not astronomical, VDWAALS too, EGB is not a number.
2) igb=2 gives something reasonable.
From these facts, one can tentatively deduce that indeed a group of atoms
is too tightly packed. This can lead to one or more negative effective Born
radii (which can never happen with igb={2,5}, but with igb=1).
To check this, one could do a single evaluation run with "rbornstat=1"
to see whether something fishy (a negative radius) turns up.
Second possibility: one could do some minimizations step with igb=2
and then start with igb=1 and see whether the problem is still there.

good luck
Andreas

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