Dear everyone,
I have some problems with relaxation of my system. Could you please help me with this issue?
I defined a cylinder with the following commands:
units metal
dimension 3
boundary s s p
atom_style atomic
lattice fcc 4.0800
region rwire cylinder z 0 0 10 0 44
create_box 1 rwire
create_atoms 1 region rwire
group wire region rwire
Then I want to relax my metal cylinder with ‘fix nvt’ and ‘minimize’ commands. The potential used here is Au_u3.eam. The units are metal and the boundary conditions are s s p. The system has 55308 atoms. And the commands used for relaxation are a combination of the following two commands groups:
min_style cg
minimize 0 0 100000 100000
And
timestep 0.001
fix nvt_relax wire nvt temp 300 300 0.1 drag 0.2
run 100000
unfix nvt_relax
I have tried three possible combinations:
(1) Minimize first and then use fix nvt. Final value of pe, ke and total energy is: -212224.34eV, 2127.3328 eV, -210097.01 eV.
(2) Fix nvt first and then minimize. Final value of pe, ke and total energy is: -212380.36 eV, 1832.117 eV, -210548.24 eV.
(3) Minimize first, then fix nvt, at last minimize again. Final value of pe, ke and total energy is: -214435.43 eV, 2127.3328 eV, -212308.09 eV.
The potential energy, kinetic energy and total energy are monitored. The change of these values is shown in the attachments. It seems if there is no ‘minimize’ after ‘fix nvt’, the pe and total energy would not get a relative low value. Should I use minimization first or nvt ensemble at a constant temperature first?
Could you please tell me whether I used a right method to relax my system? And what should be taken into account to say that the relaxation is good enough? Is there something different when a free surface is relaxed compared to periodic boundary?
Any help would be much appreciated!
With My Best Regards
Liu
pe_min_fix.eps (30.9 KB)
ke_min_fix.eps (30.9 KB)
toteng_min_fix.eps (31 KB)
pe_fix_min.eps (31 KB)
ke_fix_min.eps (31.1 KB)
toteng_fix_min.eps (31.1 KB)
pe_min_fix_min.eps (31 KB)
ke_min_fix_min.eps (31 KB)
toteng_min_fix_min.eps (31.1 KB)