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Molecular Dynamics simulation of a small molecule
you@eulerX ~$ module load new cp2k
and to submit the job:
you@eulerX ~$ bsub < jobname
Download the 4.1 exercise into your $HOME folder and unzip it:
you@eulerX ~$ wget http://www.cp2k.org/_media/exercises:2015_ethz_mmm:exercise_4.1.zip you@eulerX ~$ unzip exercises:2015_ethz_mmm:exercise_4.1.zip you@eulerX ~$ cd exercise_4.1
You will start from a configuration already computed in the second lecture (inp.a.pdb) which is included in the repository of this exercise as well. Use the file inp.nve for the first simulation, which is a constant energy simulation.
- md_part.inp.nve
&MD ! This section defines the whole set of parameters needed perform an MD run. ENSEMBLE NVE ! The ensemble/integrator that you want to use for MD propagation STEPS 100000 ! The number of MD steps to perform TIMESTEP [fs] 1.0 ! The length of an integration step TEMPERATURE 100.0 ! The temperature in K used to initialize the velocities with init and pos restart velocities &END MD
- Perform a constant energy simulation, 100000 time steps, with a time step of 1 fs.
you@eulerX ~$ bsub cp2k.popt -i inp.nve -o out.nve
- Using a different input file, modify the time step and the name of the project. Do it for 0.1, 2, 3, 4 fs.
- Access the corresponding *.ener files. How is the energy conservation? How is the behavior of potential and kinetic energy, and how the temperature?
- Perform now a constant Temperature simulation. The system is in contact with a thermostat, and the conserved quantity includes the thermostat degrees of freedom. The first simulation is done at 100 K: inp.100
- Then, perform a simulation at 300 K, using the restart file from the previous simulation: inp.300.
- Now you have some outputs to study with vmd.
The trajectory files we are going to study are
nve_md-pos-1.pdb md.100-pos-1.pdb md.300-pos-1.pdb
“Fire” vmd, for example vmd nve_md-pos-1.pdb From the Extensions menu, you can choose the Tk console. And from there, you can enter
source "dihedrals.vmd"
which will define the two dihedrals phi and psi. You can also pick from the extensions the “RMSD trajectory tool” and use it to align the molecule along the trajectory. Remember to replace “protein” with “all” in the selection, and then use “align”. You will see that now the molecule is well aligned along the path.
Using “Labels” menu, plot now the two dihedral angles graph.