[email protected] wrote:
Hi Carsten:

Thank you for your answers. I don't know whether I am right to reply to [email protected] <mailto:[email protected]>. If I am wrong, please tell me.


Yes, keep all discussions on the list for archival purposes (plus, other users can weigh in with advice).

As in my last letter, I said I was not able to set "*pull_weights1*" correctly. I have red the mannual, but I don't understand what it tells. I'll do with your recommendation, setting one pull group which contains 700 atoms and using Gromacs-4.0.7. Then how to set the "*pull_weights1*" ?


If you have a single pull group with 700 atoms, then you can leave pull_weights1 alone - leave it to its default value (which I believe is 0) by not even specifying it in the .mdp file.

-Justin

Best regards!

Hi,

you should set one pull group, not 700. The number of atoms in your
pull group is 700. Freezing the pull group in x and y direction probably
does what you want. Please also consider to upgrade to 4.0.7,
which is the most recent stable version.

Best,
  Carsten


On Jan 22, 2010, at 7:41 AM, [email protected] wrote:

 > Dear all:
 >        I’m using Gromacs-4.0.5 and I want to use the pull code to pull a 
slab of griphene to move along the Z direction in the simulation (Steered 
Molecular Dynamics-SMD). The griphene has 700 carbon atoms and the positions of 
the 700 atoms are expected to be immobile in the X and Y direction.
 > The following is the PULL CODE in my mdp file. However, when I used this 
code for my simulation the error always came out as “Number of weights (1) for 
pull group 1 'sla' does not match the number of atoms (700)”.
 > So here are my doubts about this simulation:
 > 1.       Can Gromacs-4.0.5 do this for me, especially keeping the C atoms 
immobile in X and Y direction while moving along the Z direction?
 > 2.       In my simulation, every carbon atom in the slab of griphene was 
defined as a group. Is it right?
 > 3.       How to give the “pull_weights1” to avoid the above ERROR?
 > Any suggestions and answers are welcome. Thank you in advance!
> > ; COM PULLING > ; Pull type: no, umbrella, constraint or constant_force
 > pull                     = constant_force
 > ; Pull geometry: distance, direction, cylinder or position
 > pull_geometry            = distance
 > ; Select components for the pull vector. default: Y Y Y
 > pull_dim                 = N N Y
 > ; Cylinder radius for dynamic reaction force groups (nm)
> pull_r1 = > ; Switch from r1 to r0 in case of dynamic reaction force > pull_r0 = > pull_constr_tol = 1e-06
 > pull_start               = no
 > pull_nstxout             = 10
 > pull_nstfout             = 10
> ; Number of pull groups > pull_ngroups = 700
 > ; Group name, weight (default all 1), vector, init, rate (nm/ps), 
kJ/(mol*nm^2)
> pull_group0 = > pull_weights0 = > pull_pbcatom0 = > pull_group1 = sla
 > pull_weights1            = 1
 > pull_pbcatom1            = 0
 > pull_vec1                = 0.0 0.0 1.0
 > pull_init1               = 0.0
 > pull_rate1               = 0
 > pull_k1                  = 1.2e-4
 > pull_kB1                 = 0


--
========================================

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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