mirror of https://github.com/lammps/lammps.git
88 lines
2.8 KiB
Plaintext
88 lines
2.8 KiB
Plaintext
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------- To view a lammps trajectory in VMD --------
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1) Build a PSF file for use in viewing with VMD.
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This step works with VMD 1.9 and topotools 1.2.
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(Older versions, like VMD 1.8.6, don't support this.)
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a) Start VMD
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b) Menu Extensions->Tk Console
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c) Enter:
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(I assume that the the DATA file is called "system.data")
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topo readlammpsdata system.data full
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animate write psf system.psf
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2)
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Later, to Load a trajectory in VMD:
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Start VMD
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Select menu: File->New Molecule
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-Browse to select the PSF file you created above, and load it.
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(Don't close the window yet.)
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-Browse to select the trajectory file.
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If necessary, for "file type" select: "LAMMPS Trajectory"
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Load it.
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---- A note on trajectory format: -----
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If the trajectory is a DUMP file, then make sure the it contains the
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information you need for pbctools (see below. I've been using this
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command in my LAMMPS scripts to create the trajectories:
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dump 1 all custom 5000 DUMP_FILE.lammpstrj id mol type x y z ix iy iz
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It's a good idea to use an atom_style which supports molecule-ID numbers
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so that you can assign a molecule-ID number to each atom. (I think this
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is needed to wrap atom coordinates without breaking molecules in half.)
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Of course, you don't have to save your trajectories in DUMP format,
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(other formats like DCD work fine) I just mention dump files
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because these are the files I'm familiar with.
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3) ----- Wrap the coordinates to the unit cell
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(without cutting the molecules in half)
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a) Start VMD
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b) Load the trajectory in VMD (see above)
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c) Menu Extensions->Tk Console
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d) Try entering these commands:
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pbc wrap -compound res -all
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pbc box
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----- Optional ----
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Sometimes the solvent or membrane obscures the view of the solute.
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It can help to shift the location of the periodic boundary box
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To shift the box in the y direction (for example) do this:
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pbc wrap -compound res -all -shiftcenterrel {0.0 0.15 0.0}
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pbc box -shiftcenterrel {0.0 0.15 0.0}
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Distances are measured in units of box-length fractions, not Angstroms.
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Alternately if you have a solute whose atoms are all of type 1,
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then you can also try this to center the box around it:
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pbc wrap -sel type=1 -all -centersel type=2 -center com
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4)
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You should check if your periodic boundary conditions are too small.
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To do that:
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select Graphics->Representations menu option
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click on the "Periodic" tab, and
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click on the "+x", "-x", "+y", "-y", "+z", "-z" checkboxes.
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5) Optional: If you like, change the atom types in the PSF file so
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that VMD recognizes the atom types, use something like:
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sed -e 's/ 1 1 / C C /g' < system.psf > temp1.psf
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sed -e 's/ 2 2 / H H /g' < temp1.psf > temp2.psf
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sed -e 's/ 3 3 / P P /g' < temp2.psf > system.psf
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(If you do this, it might effect step 2 above.)
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