vinothkumar mohanakrishnan wrote:
Hi justin

I found what went wrong and i corrected my mdp file.now the system equilibrated to the desired temperature 300 K (plus r minus 30 K) is this ok?

This is impossible to assess without seeing your .mdp settings. A fluctuation of 10% is probably fine.

Apart from that i want to know how you plot the average running pressure and density in your tutorial for lyzosyme (redline). i just want to do that for DCE. any help is highly appreciated.


Xmgrace.

-Justin

Regards
Vinoth

On Wed, Oct 20, 2010 at 5:33 PM, Justin A. Lemkul <jalem...@vt.edu <mailto:jalem...@vt.edu>> wrote:



    vinothkumar mohanakrishnan wrote:

        Hi Justin

        I corrected the mistake what you said and i am able to run
        energy minimisation and equilibration. but when i view my em.gro
        and equilibration.gro in VMD it seems to me that the bonds
        between the atoms are broken in molecules.I used g_energy to
        check weather the system has


    VMD tries to guess where bonds should be, but does not always do a
    good job. Your topology defines bonds.  These are the only bonds
    that there will be.  None can be broken or formed in standard MD.


        equilibrated to the required temperature (300K) i found that the
        variation in the temperature was 100K (plus r minus) . i am not
        able find out what went wrong. any help is highly appreciated.


    Without seeing your .mdp file, there's no way to know.  The
    fluctuation does seem too high, though, unless your system really is
    just that unstable.  Are other properties converged - potential
    energy, density, etc?  What type of ensemble are you using?

    -Justin

        Regards
        Vinoth


        On Mon, Oct 18, 2010 at 6:09 PM, Justin A. Lemkul
        <jalem...@vt.edu <mailto:jalem...@vt.edu>
        <mailto:jalem...@vt.edu <mailto:jalem...@vt.edu>>> wrote:



           vinothkumar mohanakrishnan wrote:

               Dear Justin

               what corrections i should make to ffoplsaan.itp to make it
               correct. what i should give instead of CAB and CLAA?.


           You must use atom types, not names.  Unfortunately, you've
        chosen to
           use atom names, which are also types, which makes all of this
        quite
           confusing if you're not sure what you're doing.

           You defined two new atom types - opls_966 (CAB) and opls_967
        (CLAA),
           which are the only indicators you are allowed to use if
        introducing
           new types.  Thus, references to atom names (CAC, CLAD) will
        generate
           fatal errors.


               i copied the .rtp .atp .itp files from
               usr/local/gromacs/share/gromacs/top to my working
        directory and
               added these parameters to the corresponding files. what
        you mean
               is should i need to add these parameters to the source
        directory
               ( usr/local/gromacs/share/gromacs/top)?


           Your topology needs to be consistent with whatever files need
        to be
           included. By default, Gromacs checks the working directory first,
           but if you've moved to a new (sub)directory to carry out further
           steps, the grompp will not find your modified files, but will
           instead locate only the default force field files in $GMXLIB.
            Either keep all your work in one directory (which can get
        messy),
           or make use of the "include" keyword in the .mdp file.  Any
           directory specified there will be searched after the working
           directory, but before $GMXLIB.

           -Justin

               Regards
               Vinoth


               On Mon, Oct 18, 2010 at 5:27 PM, Justin A. Lemkul
               <jalem...@vt.edu <mailto:jalem...@vt.edu>
        <mailto:jalem...@vt.edu <mailto:jalem...@vt.edu>>
               <mailto:jalem...@vt.edu <mailto:jalem...@vt.edu>
        <mailto:jalem...@vt.edu <mailto:jalem...@vt.edu>>>> wrote:



                  vinothkumar mohanakrishnan wrote:

                      Hi all

                      i added new atomtype for dichloroethane (DCE) and
        added the
                      corresponding parameters in the .rtp, .atp,
        .bon.itp, .nb.itp
                      respectively. given below are my additions to the
               corresponding
                      files respectively.

                      *ffoplsaa.rtp*

                      [ DCE ]
                       [ atoms ]
                       CLAA opls_967 -0.2270  1
                       CAB  opls_966  0.2270  1
                       CAC  opls_966  0.2270  2
                       CLAD opls_967 -0.2270  2

                      [ bonds ]
                       CLAA    CAB
                       CAB    CAC
                       CAC    CLAD

                      [ angles ]
                       CLAA    CAB    CAC
                       CAB    CAC    CLAD

                      [ dihedrals ]
                       CLAA    CAB    CAC    CLAD

                      *ffoplsaa.atp*

                       opls_966   14.02700  ; CH2 for DCE
                       opls_967   35.45300  ; CL for DCE

                      *ffoplsaabon.itp*

                      [bondtypes]
                      CLAA  CAB     1    0.17870   194137.6   ; CL-CH2
        for DCE
                      CAB   CAC     1    0.15300   259408.0   ; CH2-CH2
        for DCE
                      CAC   CLAD    1    0.17870   194137.6   ; CL-CH2
        for DCE

                      [angletypes]
                      CLAA  CAB   CAC       1   108.200    368.192   ;
        C-C-CL
               for DCE
                      CAB   CAC   CLAD      1   108.200    368.192   ;
        C-C-CL
               for DCE

                      [dihedraltypes]
                      CLAA   CAB     CAC   CLAD     3     20.76096
         -0.4184                 27.011904  0.00000   0.00000   0.00000
        ; for DCE


                  You shouldn't be using atom names in the [*types]
        directives.
                What
                  you should be using are the interpolated types from
               ffoplsaanb.itp,
                  thus you have only utilized opls_966 (CAB) and
        opls_967 (CLAA).

                      *ffoplsaanb.itp*


opls_966 CAB 6 14.02700 0.227 A 3.98000e-01
                       4.76976e-01 ; CH2 of DCE
opls_967 CLAA 17 35.45300 -0.227 A 3.16000e-01
                       0.20920e+01 ; Cl of DCE

                      *dce.pdb*

HETATM 1 CLAA DCE 1 6.300 -2.280 1.360 1.00
                      20.00            CL
HETATM 2 CAB DCE 1 5.060 -3.540 1.500 1.00
                      20.00             C
HETATM 3 CAC DCE 1 4.320 -3.740 0.170 1.00
                      20.00             C
                      HETATM    4 CLAD DCE     1       3.270  -2.350
         -0.210  1.00
                      20.00            CL

                      After adding all this, when i run grompp i get the
        error as
                      *fatal error Unknown bond_atomtype CLAA*. can any
        one tell me
                      why this happens?.


                  Have you been sure to #include the correct (modified)
        force field
                  files?  That is, if you made a local copy and adjusted
        them,
               these
                  won't be the files that pdb2gmx will #include by default.

                  -Justin

                      Regards
                      Vinoth


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

                  Justin A. Lemkul
                  Ph.D. Candidate
                  ICTAS Doctoral Scholar
                  MILES-IGERT Trainee
                  Department of Biochemistry
                  Virginia Tech
                  Blacksburg, VA
                  jalemkul[at]vt.edu <http://vt.edu> <http://vt.edu>
        <http://vt.edu> | (540)

               231-9080

                  http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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

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

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

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

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

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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