[gmx-users] rotate in editconf

T.A.Wassenaar T.A.Wassenaar at rug.nl
Thu Jul 7 13:37:01 CEST 2005


Hi Attilio,

It's better not to rotate the box but to setup a new box 
for the rotated system. Gromacs indeed only allows 
triclinic boxes with the first vector aligned with the 
x-axis, the second in the xy-plane and the third with a 
positive z-component. But if you use editconf to setup a 
box around the newly created system, then everything will 
probably be fine.

Hope it helps,

Tsjerk

On Thu,  7 Jul 2005 13:09:59 +0200
  Attilio Vargiu <vargiu at sissa.it> wrote:
> Hi Tsjerk,
> first, thanks for the answer!
> I already tried to generate a new box, rotating also the 
>"box vectors" at the
> end of the gro file.
> But I read in the manual online that the gro format only 
>supports cubic box in
> which the box vectors coincide with the axis, so I dont 
>know how to do! In
> addition I tried to find something about g96 format, 
>without success...
> 
> 
> Scrive "T.A.Wassenaar" <T.A.Wassenaar at rug.nl>:
> 
>> 
>> Hi Attilio,
>> 
>> Do you construct a new box after rotation? editconf does 
>> not change the box when rotating a system, and besides, 
>> the box would probably be invalid anyway. So if you 
>> haven't done so, try to generate a new box for the 
>>rotated 
>> system (translation doesn't matter).
>> 
>> Hope it helps,
>> 
>> Tsjerk
>> 
>> 
>> On Wed, 06 Jul 2005 17:21:08 +0200
>>   Attilio <vargiu at sissa.it> wrote:
>> > Hi all,
>> > 
>> > I'm trying to implement umbrella sampling on my 
>>system.
>> > My reaction coordinate is a distance between two atoms 
>>A 
>> >and B.
>> > Before starting the dynamics I rotated the system in 
>> >order to align the vector AB with the z axis. To 
>> >rototranslate the system I used editconf with the flag 
>> >-rotate.
>> > In this manner I apply an harmonic constraint only in 
>> >the z direction, allowing the system to explore phase 
>> >space in the xy plane. This is my pull.ppa file:
>> > 
>> > verbose = yes
>> > runtype=umbrella
>> > group_1=C_IMI
>> > reference_group=N_GUA
>> > reftype=com
>> > weights_1=
>> > pulldim=N N Y
>> > k1=15000;kJ/mol-1/nm-2
>> > pos1= 0 0 0.422
>> > 
>> > But the dynamics died after 1-2 min, with this error:
>> > 
>> > There are 24895 atoms in your xtc output selection
>> > 
>> > t = 0.000 ps: Water molecule starting at atom 12323 
>>can 
>> >not be settled.
>> > Check for bad contacts and/or reduce the 
>>timestep.Wrote 
>> >pdb files with previous and current coordinates
>> > Large VCM(group IMI):     -0.05608,     -0.16218, 
>> >    -0.08893, ekin-cm:  5.55321e+00
>> > Group IMI with mass  2.97308e+02, Ekrot  6.00893e+00 
>> >Det(I) =  1.31027e+02
>> >  COM:      4.21794       4.56359       3.70009
>> >  P:      -16.67273     -48.21760     -26.44075
>> >  V:       -0.05608      -0.16218      -0.08893
>> >  J:       11.75914     -12.46278      17.04114
>> >  w:        0.39515      -0.24657       0.25223
>> > Inertia tensor (3x3):
>> >   Inertia tensor[    0]={ 3.36886e+01, -1.93692e+00, 
>> >-1.95062e+01}
>> >   Inertia tensor[    1]={-1.93692e+00,  9.88940e-01, 
>> > 2.37864e+00}
>> >   Inertia tensor[    2]={-1.95062e+01,  2.37864e+00, 
>> > 1.75272e+01}
>> > Long Range LJ corr. to Epot:   -891.161, Pres: 
>> >  -118.079, Vir:    5346.96
>> >   Energies (kJ/mol)
>> >           Bond       G96Angle    Proper Dih. 
>> >         LJ-14     Coulomb-14
>> >    8.73471e+02    1.88436e+03    2.22140e+03 
>> >   8.62560e+02   -1.32192e+04
>> >        LJ (SR)  Disper. corr.   Coulomb (SR)   Coulomb 
>> >(LR) Position Rest.
>> >    4.79055e+17   -8.91161e+02   -3.15962e+05 
>> >  -2.24687e+04    0.00000e+00
>> >      Potential    Kinetic En.   Total Energy 
>> >   Temperature Pressure (bar)
>> >    4.79055e+17            nan            nan 
>> >           nan            nan
>> > 
>> > 
>> > t = 0.000 ps: Water molecule starting at atom 12446 
>>can 
>> >not be settled.
>> > Check for bad contacts and/or reduce the 
>>timestep.Wrote 
>> >pdb files with previous and current coordinates
>> > 
>> > t = 0.000 ps: Water molecule starting at atom 12446 
>>can 
>> >not be settled.
>> > ..........
>> > ..........
>> > Check for bad contacts and/or reduce the 
>>timestep.Wrote 
>> >pdb files with previous and current coordinates
>> > Check for bad contacts and/or reduce the 
>>timestep.Wrote 
>> >pdb files with previous and current coordinates
>> > 
>> > t = 0.001 ps: Water molecule starting at atom 12446 
>>can 
>> >not be settled.
>> > Check for bad contacts and/or reduce the 
>>timestep.Wrote 
>> >pdb files with previous and current coordinates
>> > Grid: -2147483648 x -2147483648 x -2147483648 cells
>> >Fatal error: ci = -1 should be in 0 .. -1 [FILE 
>>nsgrid.c, 
>> >LINE 218]
>> > 
>> > Then I tried to run the original (without 
>> >rototranslation) system, and this works without 
>>problems 
>> >(I tried both a normal dynamics and the one with the 
>> >umbrella code).
>> > Incidentally I visualized with VMD both the system, 
>>and 
>> >it seems that periodic conditions are not well 
>>conserved 
>> >in the rototranslated system. In fact a simulation of 
>> >this latter without periodic conditions proceed well.
>> > 
>> > Does anybody kwow how to deal with this problem?
>> > Many thanks in advance,
>> > 
>> > Attilio
>> > 
>> > -- 
>> > Attilio Vittorio Vargiu
>> > PhD Student at SISSA/ISAS
>> > via Beirut 4
>> > I-34014 Trieste, Italy
>> > tel +390403787335   fax +390403787528
>> > 
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