[gmx-users] Giving an initial velocity to a group of atoms

Jashimuddin Ashraf jashimuddin.ashraf23 at gmail.com
Mon May 11 17:03:12 CEST 2015


Thanks again for your reply Dr. Lemkul.

I was also expecting a disaster because I gave an unrealistic starting
velocity of the structure. But the simulation was running fine. I tried
using the gmxdump and found that the velocities I am getting are not the
velocities I've given to the atoms.

In your reply you were kind to reply that "You need to use proper formatting
"

I am following the format in the lilnk -

http://chembytes.wikidot.com/g-grofile

what I did was I just added 3 extra columns to my .gro file manually after
getting .gro file from editconf. What might be my problem?


Thanks in advance.

On Sun, May 3, 2015 at 10:24 PM, Justin Lemkul <jalemkul at vt.edu> wrote:

>
>
> On 5/3/15 5:51 AM, Jashimuddin Ashraf wrote:
>
>> Thanks for your reply Dr. Lemkul. I was simulating a small carbon nanotube
>> to test the idea. So, I added three extra columns after the coordinates
>> inside my .gro file like this-
>>
>> ==================================================
>> ============================================
>> Georgetown Riga Oslo Madrid Amsterdam Chisinau Stockholm
>>     64
>>      1C        C    1  10.539  10.000  10.061 1     0 0
>>      1C        C    2  10.534  10.070  10.183 1     0 0
>>      1C        C    3  10.539  10.000   9.817   1     0 0
>>      1C        C    4  10.498  10.206   9.939 1     0 0
>>      1C        C    5  10.534  10.070   9.939 1     0  0
>>      1C        C    6  10.466  10.269  10.061 1     0 0
>>      1C        C    7  10.498  10.206  10.183 1     0 0
>>      1C        C    8  10.381  10.381   9.817 3     0 0
>>      1C        C    9  10.466  10.269   9.817 3     0  0
>>      1C        C   10  10.328  10.427   9.939 3     0 0
>>      1C        C   11  10.381  10.381  10.061 3     0 0
>>      1C        C   12  10.206  10.498  10.183 3     0 0
>>      1C        C   13  10.328  10.427  10.183 3     0 0
>>      1C        C   14  10.139  10.520   9.817 3     0 0
>>      1C        C   15  10.206  10.498   9.939 3     0 0
>>      1C        C   16  10.000  10.539  10.061 3     0 0
>>      1C        C   17  10.139  10.520  10.061 3     0 0
>>      1C        C   18   9.930  10.534  10.183 3     0 0
>>      1C        C   19  10.000  10.539   9.817 3     0 0
>>      1C        C   20   9.794  10.498   9.939 3     0  0
>>      1C        C   21   9.930  10.534   9.939 3     0  0
>>      1C        C   22   9.731  10.466  10.061 3     0 0
>>      1C        C   23   9.794  10.498  10.183 3     0 0
>>      1C        C   24   9.619  10.381   9.817 3     0  0
>>      1C        C   25   9.731  10.466   9.817 3     0  0
>>      1C        C   26   9.573  10.328   9.939 3     0  0
>>      1C        C   27   9.619  10.381  10.061 3     0 0
>>      1C        C   28   9.502  10.206  10.183 3     0 0
>>      1C        C   29   9.573  10.328  10.183 3     0 0
>>      1C        C   30   9.480  10.139   9.817 3     0  0
>>      1C        C   31   9.502  10.206   9.939 3     0  0
>>      1C        C   32   9.461  10.000  10.061 3     0 0
>>      1C        C   33   9.480  10.139  10.061 3     0 0
>>      1C        C   34   9.466   9.930  10.183 3     0  0
>>      1C        C   35   9.461  10.000   9.817 3     0  0
>>      1C        C   36   9.502   9.794   9.939 3     0  0
>>      1C        C   37   9.466   9.930   9.939 3     0  0
>>      1C        C   38   9.534   9.731  10.061 3     0  0
>>      1C        C   39   9.502   9.794  10.183 3     0  0
>>      1C        C   40   9.619   9.619   9.817 3     0  0
>>      1C        C   41   9.534   9.731   9.817 3     0  0
>>      1C        C   42   9.672   9.573   9.939 3     0  0
>>      1C        C   43   9.619   9.619  10.061 3     0  0
>>      1C        C   44   9.794   9.502  10.183 3     0  0
>>      1C        C   45   9.672   9.573  10.183 3     0  0
>>      1C        C   46   9.861   9.480   9.817 3     0  0
>>      1C        C   47   9.794   9.502   9.939 3     0  0
>>      1C        C   48  10.000   9.461  10.061 3     0 0
>>      1C        C   49   9.861   9.480  10.061 3     0  0
>>      1C        C   50  10.070   9.466  10.183 3     0 0
>>      1C        C   51  10.000   9.461   9.817 3     0  0
>>      1C        C   52  10.206   9.502   9.939 3     0  0
>>      1C        C   53  10.070   9.466   9.939 3     0  0
>>      1C        C   54  10.269   9.534  10.061 3     0 0
>>      1C        C   55  10.206   9.502  10.183 3     0 0
>>      1C        C   56  10.381   9.619   9.817 3     0  0
>>      1C        C   57  10.269   9.534   9.817 3     0  0
>>      1C        C   58  10.427   9.672   9.939 3     0  0
>>      1C        C   59  10.381   9.619  10.061 3     0 0
>>      1C        C   60  10.498   9.794  10.183 3     0 0
>>      1C        C   61  10.427   9.672  10.183 3     0 0
>>      1C        C   62  10.520   9.861   9.817 3     0  0
>>      1C        C   63  10.498   9.794   9.939 3     0  0
>>      1C        C   64  10.520   9.861  10.061 3     0 0
>>    20.00000  20.00000  20.00000
>> ==================================================
>> ============================================
>>
>>
> You need to use proper formatting; check the .tpr with gmx dump to verify
> that you're getting what you think you're getting.
>
>  but my simulation does not seem to have any effect of this. I tried
>> increasing the value but it did not change the results. How can I solve
>> this?
>>
>>
> How are you assessing the success or failure of what you're doing?  An MD
> simulation will quickly diverge because of its inherent chaotic nature.
>
>
> -Justin
>
> --
> ==================================================
>
> Justin A. Lemkul, Ph.D.
> Ruth L. Kirschstein NRSA Postdoctoral Fellow
>
> Department of Pharmaceutical Sciences
> School of Pharmacy
> Health Sciences Facility II, Room 629
> University of Maryland, Baltimore
> 20 Penn St.
> Baltimore, MD 21201
>
> jalemkul at outerbanks.umaryland.edu | (410) 706-7441
> http://mackerell.umaryland.edu/~jalemkul
>
> ==================================================
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