LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Mailing List Archives
[lammps-users] issues in system equilibration
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[lammps-users] issues in system equilibration


From: Mohit Sharma <mohit3013@...24...>
Date: Thu, 12 Apr 2018 22:51:34 +0800

Dear LAMMPS users

I am trying to use LAMMPS for indentation analysis of copper by diamond indenter. I am using hybrid pair style, and fix move command to move a spherical rigid region as indenter.

The issue is the copper structure is fluctuating inconsistently. The forces are also inconsistent; the unloading forces are negative from starting.

I would appreciate some expert advice on following considerations.

1.      Using four atoms types 1-3 copper (for visualizing boundary w_mobile, w_thermostat, w_boundary) and 4 diamond

pair_style            hybrid tersoff eam morse 2.5658

pair_coeff           * * tersoff SiC.tersoff NULL NULL NULL C

pair_coeff           1*3 4 morse 0.087 5.14 2.05 9.025

pair_coeff           1*3 1*3 eam Cu_u3.eam

my intention is to apply tersoff for all interactions, then override Cu-C as morse and Cu-Cu as eam. So the remaining C-C will be tersoff.

2.      Creating velocity at 300K and applying nve ensemble

velocity                w_mobile create 300.0 12345 temp tmobile          

run                        0

velocity                w_mobile scale 300.0

fix                          1 w_mobile nve

fix                          2 w_thermostat nve

fix                          3 all temp/rescale 1 300.0 300.0 0.1 1.0

fix                          4 w_boundary setforce 0.0 0.0 0.0

fix                          5 i_diamond rigid single

.

.

unfix                     3

fix                          3 w_thermostat temp/rescale 1 300 300 0.1 1.0

3.      Can a region be considered rigid if applying no fix on the region? Or should apply fix rigid.

Using fix rigid command causing atom lost error.  

4.      Is fix move command adequate for the indentation purpose?

5.      Using 

a.      variable   fz equal fcm(i_diamond,z)                        for force on indenter

b.      variable depthz equal xcm(i_diamond,z)                for position of indenter

 

I am using periodic boundary in x, y and non-periodic fixed boundary for z

·        Version: LAMMPS 64-bit 16Mar2018

 

 

Regards 

Mohit Sharma

Precision Manufacturing Lab 

NTUST, Taipei Taiwan