LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Mailing List Archives
Re: [lammps-users] How to make a supercooled liquid by LAMMPS
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [lammps-users] How to make a supercooled liquid by LAMMPS


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Tue, 29 Aug 2017 09:14:18 -0400



On Tue, Aug 29, 2017 at 6:52 AM, bahman daneshian <bahmanpbamp@...24...> wrote:
Dear Lammpsers, 

I would like to have a supercooled melt at 1156K. 

As you can see below, I used fix temp/rescale for fast cooling of the system and then let  the system a 7000 time steps to reach to  equilibrium under NVT ensemble .
 But, when I plot the potential energy versus time curve, I cannot see a non-equilibrium condition at the beginning of potential energy curve which indicating to the initial non equilibrium condition.it meen that I couldnot access to the supercooled melt. 

to have a supercooled melt, you need a proper melt first.
​your input starts from a crystal structure. can you melt a crystal melt in 100 fs? and by using an nose-hoover thermostat?
by considering the experimental melting point instead of the one for your EAM potential?
by using a target temperature barely above that assumed melting point?
by setting an initial kinetic energy far below that target temperature?

where have you learned your MD?? 
you need proper training, help and guidance. a *lot* of it.
much more than you can ever get from this list.

axel.


So, any helpful comment  is highly appreciated. 



#Phase 1 ------------------------------------------Simulation main setup----------------------------------
dimension      3
units   metal               # if you select units metal, distance are based on Ang
atom_style     atomic
boundary       p p p               # if you select dimension2, you have to select boundary as ppp.
lattice        fcc  3.6150        #3.6147 is Cu unit cell size in Ang as per units metal


#simulation box is simulbox 
region simulbox block 0 10  0 10 0 10 #units box                  
create_box   2 simulbox   #2 is number of atoms types
create_atoms 1 box
mass     1  63.550 #mass must always be defined after create_box
mass     2 63.550


velocity all create 300 300
pair_style eam #You can use an alloy EAM file for just a single element.
pair_coeff * * Cu_u3.eam
neighbor 2.5 bin
neigh_modify every 20 delay 0 check no

fix 1 all npt temp 1375.0 1375.0 0.01 iso 1.01325 1.01325 1.01325   # Cu melting point 1358K
thermo 100
dump  1 all image 500 image.*.png  type  type  adiam 1.5 axes yes 0.8 0.02 zoom 1.0 view 80 -30
dump_modify 1 backcolor white boxcolor white acolor 1*2 blue/red/orange/green/cyan/aqua/yellow/red
run 100
unfix 1


fix 2 all temp/rescale 100 1375 1156 0.02 1.0
run 1000

fix 3 all nvt temp 1156.0 1156.0 0.01 # Tdamp must be 100 timetep =100*0.001=0.1
thermo 100
dump  3 all image 500 image.*.png  type  type  adiam 1.5 axes yes 0.8 0.02 zoom 1.0 view 80 -30
dump_modify 3 backcolor white boxcolor white acolor 1*2 blue/red/orange/green/cyan/aqua/yellow/red
run 5000
unfix 3


Regards,
B. D

------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
_______________________________________________
lammps-users mailing list
lammps-users@...655....net
https://lists.sourceforge.net/lists/listinfo/lammps-users




--
Dr. Axel Kohlmeyer  akohlmey@...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.