Temperature rise very sharp making system unstable.

Hello Lammps users,

I am very new in using lammps.I wanted to simulate a system using the parameters exactly given in literature but having a lot of problems and the temperature steeps up so sharply making the system to blow off.plz help.i am giving the input file and part of log file…

#LAMMPS Input file for xxx

----------------- Init Section -----------------

units metal
atom_style full
pair_style buck/long/coul/long cut long 12.0
bond_style harmonic
angle_style harmonic
improper_style cvff
kspace_style ewald/disp 0.00001

----------------- Atom Definition Section -----------------

read_data data.xxx

----------------- Settings Section -----------------

bond_coeff 1 400.0 1.29
angle_coeff 1 9.3179 120.0
improper_coeff 1 1.1392 1 1
pair_coeff 1 1 0.0 1.0 0.0
pair_coeff 1 3 0.0 1.0 0.0
pair_coeff 3 3 0.0 1.0 0.0
pair_coeff 2 3 0.0 1.0 0.0
pair_coeff 2 2 360108 0.19756 0.0
pair_coeff 1 2 8839.3 0.23813 0.0
velocity all create 300.0 4928459 rot yes dist gaussian
fix fxnve all nve

fix fxnpt all npt temp 300.0 300.0 100.0 iso 1.0 1.0 1000.0 drag 1.0

fix fxnvt all nvt temp 300.0 300.0 500.0 tchain 1

timestep 0.001

----------------- Output Section -----------------

thermo 1
thermo_style custom step temp ke pe etotal vol cella cellb cellc cellalpha cellbeta cellgamma
dump dump1 all custom 100 dump*.xyz id x y z

----------------- Execution Section -----------------

run 100

see how temperature creeps up!
Step Temp KinEng PotEng TotEng Volume Cella Cellb Cellc CellAlpha CellBeta CellGamma
0 300 83.721796 -11997.065 -11913.343 26480.128 29.934 29.934 34.124 90 90 120
1 466.98272 130.32211 -12040.096 -11909.774 26480.128 29.934 29.934 34.124 90 90 120
2 1025.6263 286.22424 -12200.894 -11914.669 26480.128 29.934 29.934 34.124 90 90 120
3 1803.4706 503.29933 -12419.391 -11916.092 26480.128 29.934 29.934 34.124 90 90 120
4 2682.9522 748.7386 -12666.037 -11917.298 26480.128 29.934 29.934 34.124 90 90 120
5 3548.4757 990.28254 -12913.077 -11922.795 26480.128 29.934 29.934 34.124 90 90 120
6 4223.7675 1178.738 -13097.117 -11918.379 26480.128 29.934 29.934 34.124 90 90 120
7 4841.6543 1351.1733 -13271.392 -11920.218 26480.128 29.934 29.934 34.124 90 90 120
8 5421.1371 1512.8911 -13430.162 -11917.271 26480.128 29.934 29.934 34.124 90 90 120
9 6033.0696 1683.6647 -13601.79 -11918.125 26480.128 29.934 29.934 34.124 90 90 120
10 6643.3448 1853.9759 -13771.111 -11917.135 26480.128 29.934 29.934 34.124 90 90 120
11 7317.1017 2042.003 -13953.017 -11911.014 26480.128 29.934 29.934 34.124 90 90 120
12 8268.4498 2307.4982 -14222.419 -11914.921 26480.128 29.934 29.934 34.124 90 90 120
13 9466.0542 2641.7168 -14552.382 -11910.665 26480.128 29.934 29.934 34.124 90 90 120
14 11116.299 3102.2552 -15009.404 -11907.149 26480.128 29.934 29.934 34.124 90 90 120
15 13557.163 3783.4334 -15674.924 -11891.491 26480.128 29.934 29.934 34.124 90 90 120
16 17117.816 4777.1142 -16612.731 -11835.617 26480.128 29.934 29.934 34.124 90 90 120
17 21664.852 6046.0677 -16971.533 -10925.466 26480.128 29.934 29.934 34.124 90 90 120
18 29504.115 8233.7918 -16850.688 -8616.8962 26480.128 29.934 29.934 34.124 90 90 120
19 43160.224 12044.838 -17671.226 -5626.3873 26480.128 29.934 29.934 34.124 90 90 120
20 60682.691 16934.88 -16230.357 704.52294 26480.128 29.934 29.934 34.124 90 90 120
21 79434.358 22167.957 -14312.611 7855.3457 26480.128 29.934 29.934 34.124 90 90 120
22 122829.99 34278.491 -13246.911 21031.579 26480.128 29.934 29.934 34.124 90 90 120
23 162119.83 45243.211 -6923.666 38319.545 26480.128 29.934 29.934 34.124 90 90 120

plz help.

Thanking you

Your temperature jumps by 50% in one timestep.
Usually that indicates a bad input config, e.g. with
overlapping atoms, so that your dynamics are bad.

You can try using the minimize command first.

Steve