[lammps-users] Total energy

Hello!

There is a problem with total energy and a pressure. Why it is changing?

LAMMPS (21 May 2008)
Lattice spacing in x,y,z = 35.2 35.2 35.2
Created orthogonal box = (0 0 -0.1) to (7500 750 0.1)
  8 by 1 by 1 processor grid
Created 4708 atoms
4708 atoms in group argon
Deleted 185 atoms, new total = 4523
Setting up run ...
Memory usage per processor = 1.7592 Mbytes
Step Temp E_pair E_mol TotEng Press
       0 299.21877 1199.2815 0 3888.1058 126.68302
    1000 432.62702 0 0 3887.6508 47.390231
    2000 432.75828 0 0 3888.8303 47.404609
    3000 431.8336 12.726607 0 3893.2475 48.633311
    4000 433.38735 0.33918928 0 3894.8224 47.57826
    5000 433.12921 0.32006204 0 3892.4835 47.582922
    6000 433.78887 2.8944793 0 3900.9858 48.006868
    7000 433.93886 1.5558633 0 3900.995 47.826188
    8000 434.68981 3.3958756 0 3909.5831 48.074572
    9000 434.70286 3.0361277 0 3909.3407 48.082897
   10000 435.44562 1.5805573 0 3914.5596 48.10281
   11000 435.90017 1.4835493 0 3918.5473 48.105203
   12000 435.88357 5.2336045 0 3922.1481 48.705453
   13000 436.26564 2.5428759 0 3922.8908 48.42991
   14000 436.35565 1.6956182 0 3922.8523 48.143377
   15000 435.91511 5.6677653 0 3922.8658 48.727619
   16000 436.12945 3.7412719 0 3922.8654 48.344724
   17000 436.41915 1.1127639 0 3922.8401 48.0943
   18000 436.48242 7.9221255 0 3930.2181 48.826914
   19000 437.79983 1.9935748 0 3936.128 48.329444
   20000 437.89985 3.5566794 0 3938.5898 48.517404
   21000 438.13525 1.4449524 0 3938.5935 48.382839
   22000 439.03171 3.4092067 0 3948.6134 48.780509
   23000 439.51575 3.4210539 0 3952.9749 48.600288
   24000 439.62562 2.4226687 0 3952.9639 48.6426
   25000 440.54687 0.12981493 0 3958.9495 48.341356
   26000 440.42412 1.2181757 0 3958.9348 48.611381
   27000 440.37709 7.4421631 0 3964.7361 49.110074
   28000 440.64476 5.0429966 0 3964.7423 49.015219
   29000 441.38862 0.24673648 0 3966.6305 48.480516
   30000 441.19471 1.9880387 0 3966.6293 48.73454
   31000 440.89963 4.6391239 0 3966.6288 48.97957
   32000 441.49784 2.39913 0 3969.7644 48.842681
   33000 441.78265 4.3171695 0 3974.2418 49.093322
   34000 440.96542 12.614468 0 3975.1953 49.537741
   35000 442.46955 2.5123245 0 3978.6095 48.773345
   36000 442.48018 4.7170259 0 3980.9097 49.10993
   37000 442.42966 5.4582398 0 3981.1969 49.12861
   38000 442.75562 2.5157521 0 3981.1836 49.139631
   39000 442.51309 6.1440848 0 3982.6325 49.410867
   40000 443.08834 0.97666132 0 3982.6343 48.882058

Loop time of 25.9733 on 8 procs for 40000 steps with 4523 atoms

Pair time (\) = 0\.629694 \(2\.42439\) Neigh time \() = 0.0243819 (0.0938728)
Comm time (\) = 6\.14529 \(23\.66\) Outpt time \() = 6.44523 (24.8148)
Other time (%) = 12.7287 (49.007)

Nlocal: 565.375 ave 601 max 493 min
Histogram: 2 0 0 0 0 0 0 0 4 2
Nghost: 41 ave 47 max 37 min
Histogram: 4 0 0 0 0 0 1 0 2 1
Neighs: 125.375 ave 142 max 99 min
Histogram: 1 0 0 0 1 0 3 2 0 1

Total # of neighbors = 1003
Ave neighs/atom = 0.221755
Neighbor list builds = 102
Dangerous builds = 0

units real
dimension 2
atom_style atomic
boundary p p p

lattice sq 35.2
region box block 0 7500 0 750 -0.1 0.1 units box
create_box 1 box
create_atoms 1 box
mass 1 49.0
group argon type 1

velocity all create 300.0 87287 dist gaussian units box

pair_style lj/cut 3.4
pair_coeff 1 1 0.238 3.4 3.4
neighbor 10.0 bin
neigh_modify delay 0

region sphere1 sphere 3750 375 0 270 units box
delete_atoms region sphere1

fix 1 all nve
fix 2 all indent 10000 sphere 3750 375 0 270 vel 0.00325 0
0 units box
fix 3 all enforce2d

dump id all atom 50 dump.indent.2D
thermo 1000
timestep 0.5
run 40000

Failing to conserve total energy generally indicates the time step is too big. Try it again with a smaller time step.

Joanne

Probably b/c atoms are moving in/out of the cutoff distance. Try
pair_modify shift yes, which may help. Pressure will change when
the lattice disorders.

Steve