Dear Lammps Users,
I am conducting a project using lammps involving evaporation of water inside nanopores. One of the measurements I’m trying to take is the temperature of the water molecules (tip4p). To do this I have written a Matlab code but the answers have been off and running a test simulation of only 1000 water molecules shows answers are exactly 2/3 of the actual temperature.
Some assumptions I’ve made:
Temperature is set using ‘fix fx tip4p nvt temp 300.0 300.0 200.0’ command
Lammps temperature is given by ‘thermo_style custom step temp’ command
Matlab temperature is given by: 1/2 m v^2 = 3/2 N k T
Kinetic energy is evaluated from both hydrogen and oxygen atom velocities
N is the total number of hydrogen and oxygen atoms
Questions I have:
Is the temperature equation I’m using correct?
Should KE be derived from just oxygen atom velocity and water molecule mass or by current method?
What am I misunderstanding that leads to matlab producing 2/3 lammps result?
Attached are the results I’m obtaining and the matlab script I used along with the lammps run file (although the simulations appear to run without any issues).
Any advice you can offer is greatly appreciated.
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run.int.nvt (1.45 KB)
water_temp.m (4.5 KB)