Temperature increasing




I’ve finished pre simulation for equilibration.



I am just using results from that of pre simulation and I think that pre-simulation is enough to find stable initial condition,



because I checked that Total E, PE, KE, temp, Pressure were stable.







And when I removed thermostat, same problem occured and huge expansion of system was observed in visualization state.







In simulation, the spring is used for conneting two graphene layers and then constant angular velocity is applied only on one layer.



Do you think that this model has any significant problem?







Best regards.













--------- 원본 메일 ---------


> 보낸사람: Axel Kohlmeyer <akohlmey@…24…>
> 받는사람 : 윤홍민 <1234dndd@…1333…>
> 참조 : [email protected]
> 날짜: 2012년 5월 31일 목요일, 04시 26분 06초 +0900
> 제목: Re: [lammps-users] Temperature increasing
>
> On Wed, May 30, 2012 at 12:31 PM, 윤홍민 <1234dndd@…1333…> wrote:
> >
> > Hi all.
> >
> >
> >
> > My name is Hong Min.
> >
> >
> >
> > I want to simulate graphene.
> >
> >
> >
> > But its temperature increased dramatically and converged at abnormal
> > value.
> >
> >
> >
> > I dont know what the problem is.
>
> usually bad initial coordinates or incorrect box dimensions
> periodic cells. do a short run without a thermostat and
> writing out positions at every step and visualize it.
>
> that often immediately points out the problem.
>
> axel.
>
> axel.
>
> >
> >
> >
> > I attach my input file and logfile below.
> >
> >
> >
> > -------------input---------------------------------
> >
> > dimension 3
> > boundary p p p
> > lattice sc 0.1
> > processors 8 1 1
> >
> > units metal
> >
> > atom_style charge
> > read_data data.graphene_rotation_run2
> >
> > pair_style airebo 2.6 1 0
> > pair_coeff * * CH.airebo C
> >
> > ####################### groups / variables ###############################
> > group bottom id <= 1008
> > group upper id <> 1009 1032
> >
> > group control_x1 id = 1033
> > group control_x2 id = 1034
> > group control_y1 id = 1035
> > group control_y2 id = 1036
> >
> > group control union control_y1 control_x1 control_y2 control_x2
> > group U_C union upper control
> >
> > neigh_modify exclude group control bottom exclude group control upper
> >
> > #displace_atoms upper move 3.684 17.725 0.0 units box
> >
> > variable x equal xcm(upper,x)
> > variable y equal xcm(upper,y)
> > variable z equal xcm(upper,z)
> > variable fx equal fcm(upper,x)
> > variable fy equal fcm(upper,y)
> > variable fz equal fcm(upper,z)
> > variable fsx_y1 equal f_6[1]
> > variable fsy_y1 equal f_6[2]
> > variable fsz_y1 equal f_6[3]
> > variable fs_y1 equal f_6[4]
> > variable fsx_x1 equal f_7[1]
> > variable fsy_x1 equal f_7[2]
> > variable fsz_x1 equal f_7[3]
> > variable fs_x1 equal f_7[4]
> > variable fsx_y2 equal f_8[1]
> > variable fsy_y2 equal f_8[2]
> > variable fsz_y2 equal f_8[3]
> > variable fs_y2 equal f_8[4]
> > variable fsx_x2 equal f_9[1]
> > variable fsy_x2 equal f_9[2]
> > variable fsz_x2 equal f_9[3]
> > variable fs_x2 equal f_9[4]
> >
> > ####################### velocity / fix ###############################
> >
> > velocity all create 10.0 102486 mom yes rot yes dist gaussian units box
> >
> > fix 1 upper npt temp 10.0 10.0 1.0 iso 1.01325 1.01325 10.0
> > fix 2 all langevin 10.0 10.0 1.0 699483
> > fix 4 control momentum 1 linear 1 1 1
> > fix 5 upper addforce NULL NULL -0.6491
> >
> > fix 6 control_y1 spring couple upper 0.5 0 0 -1 INIT
> > fix 7 control_x1 spring couple upper 0.5 0 0 -1 INIT
> > fix 8 control_y2 spring couple upper 0.5 0 0 -1 INIT
> > fix 9 control_x2 spring couple upper 0.5 0 0 -1 INIT
> >
> > fix 10 control momentum 1 linear 1 1 1
> >
> > neigh_modify every 1 check yes
> >
> > ####################### output ###############################
> >
> > dump 1 all atom 100 dump_rotation_run2.gra
> >
> > thermo 100
> > thermo_style custom step ke pe etotal temp press
> >
> > timestep 0.00001
> >
> > run 10000
> > ####################### run2 ###############################
> >
> > fix 12 control move rotate 9.824 25.524 8.14 0 0 1 0.000001 units box
> > run 400000000
> > write_restart restart.graphene_rotation_run2
> >
> >
> >
> >
> > -------------------logfile-------------------------------------------------------------
> >
> > KinEng PotEng TotEng Temp
> > 1.337843 -7783.07 -7781.73 10
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> > 3.44E+12 -0.00014 3.44E+12 2.57E+13
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > ------------------------------------------------------------------------------
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> > [email protected]
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> >
>
> –
> Dr. Axel Kohlmeyer
> akohlmey@…24… http://goo.gl/1wk0
>
> College of Science and Technology
> Temple University, Philadelphia PA, USA.


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I don’t know what you mean by rotation. Point particles
don’t rotate. If you have a fix move command that is
rotating particles, you shouldn’t include those in the
temperature computation, since their motion is prescribed,
and not thermal.

Steve