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[lammps-users] Histogram of Dihedral Values
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[lammps-users] Histogram of Dihedral Values

From: Charles Belina <charles.belina@...7193...>
Date: Tue, 24 Oct 2017 18:22:06 +0300

Hey everyone,

I’m attempting to obtain a histogram of dihedral values. Since I only care about the value of a certain dihedral, I defined a group and then used a compute command:

group DiHe type 2 3 4 5 6 7 8 9
compute 1 DiHe dihedral/local phi

To get the histogram, I used:

fix DiHeCalc DiHe ave/histo 1000 9 1 0 360 180 c_1 file DiHe.histo

The simulation run time is only 20 ps (this is just a test run), and as far as I understand, this fix command should run the aforementioned compute command over the group 9 times, with the interval between measurements being 1000 time steps (1 ps). There are 180 histogram bins, each with a size of 2 degrees, starting at 0 and ending at 360. Upon running the simulation, however, the DiHe.histo file is created but is entirely empty. I received the following error in my output file:

ERROR: Illegal fix ave/histo command

I thought that I might have defined my group incorrectly, so I later ran the fix over all atoms and nevertheless received the same error. Can someone help me out please? If you needed to obtain the histogrammed values for a certain dihedral, would you even approach the problem this way? Any advice would be greatly appreciated,

Charles Belina
Student Researcher
Skolkovo Institute of Science and Technology