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[lammps-users] Position of timestep command in input file
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[lammps-users] Position of timestep command in input file

From: "Spearot, Douglas" <dspearot@...1447...>
Date: Thu, 21 Dec 2017 13:35:51 +0000



I have an input file with the general format:


1) Create box (p p p with atom_style atomic and units metal)

2) Build atoms

3) Energy Minimization (min_style cg)

4) Assign temperature and pressure via fix NPT

5) Run equilibration MD

6) Deform the lattice at a constant temperature and shear stress via fix NPT

7) Run production MD


I want to run my code with a timestep 0.001 and then again with a timestep 0.002 to check the dependence on step size.  If I place the timestep command before step 1, my deformation response in step 6 shows a major dependence on the timestep size (not good).  However, if I place my timestep command before steps 4 and 5, without making any other changes to my code, then my deformation response in step 6 is independent of the timestep size (good). 


I know that some energy minimization routines require a timestep to be specified, but as far as I understand, min_style cg is not one of them.


Any thoughts on what I might be doing wrong?  It’s been a while since I have been stumped by LAMMPS!










Douglas E. Spearot, Ph.D.

Associate Professor

Department of Mechanical & Aerospace Engineering

Herbert Wertheim College of Engineering

University of Florida

Office: NEB 133

Phone: 352-392-6747

Email: dspearot@...1447...