zero temperature in fix nvt

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1

Dear lammps users,

I perform an energy minimization on my structure with nvt and npt ensembles, but in output results lammps does not fix temperature and pressure of the system in desired values. I am using the following command:

fix opt all npt temp 298 298 100 iso 1 1 1000

This is a part of output results:

Step Temp Press PotEng KinEng TotEng Enthalpy Volume Density Atoms
0 0 8.7981061e+09 2.3384675e+10 0 2.3384675e+10 1.1692365e+11 729000 0.4274485 14473
5 0 7925674.6 21031659 0 21031659 1.0529519e+08 729000 0.4274485 14473
10 0 48899.058 97570.969 0 97570.969 617451.93 729000 0.4274485 14473
15 0 -2510.6483 -137368.68 0 -137368.68 -164061.18 729000 0.4274485 14473
20 0 264.71836 -174134.09 0 -174134.09 -171319.68 729000 0.4274485 14473
25 0 -900.61763 -184952.2 0 -184952.2 -194527.31 729000 0.4274485 14473
30 0 -3511.3207 -198108.67 0 -198108.67 -235440.04 729000 0.4274485 14473
35 0 -4484.894 -205289.18 0 -205289.18 -252971.3 729000 0.4274485 14473
40 0 -4680.5497 -208449.84 0 -208449.84 -258212.12 729000 0.4274485 14473
45 0 -5544.6645 -211251.85 0 -211251.85 -270201.15 729000 0.4274485 14473
50 0 -5571.8859 -213853.86 0 -213853.86 -273092.57 729000 0.4274485 14473
55 0 -6082.6188 -216427.83 0 -216427.83 -281096.52 729000 0.4274485 14473
60 0 -6013.8104 -219138.92 0 -219138.92 -283076.06 729000 0.4274485 14473
65 0 -5613.7899 -221389.22 0 -221389.22 -281073.45 729000 0.4274485 14473
70 0 -5311.6972 -222741.45 0 -222741.45 -279213.92 729000 0.4274485 14473
75 0 -5110.7989 -223680.42 0 -223680.42 -278016.99 729000 0.4274485 14473
80 0 -5057.3792 -224334.99 0 -224334.99 -278103.62 729000 0.4274485 14473
85 0 -4892.4897 -224863.06 0 -224863.06 -276878.63 729000 0.4274485 14473
90 0 -4893.3109 -225357.37 0 -225357.37 -277381.67 729000 0.4274485 14473
95 0 -4822.0969 -225795.62 0 -225795.62 -277062.79 729000 0.4274485 14473
100 0 -4755.5066 -226266.16 0 -226266.16 -276825.36 729000 0.4274485 14473

any help will be appreciated.

regards

Mina

2

Dear lammps users,

I perform an energy minimization on my structure with nvt and npt ensembles, but in output results lammps does not fix temperature and pressure of the system in desired values. I am using the following command:

it is not possible to do a minimization and use a thermostat at the
same time. please have a look at the documentation of fix nvt and see
that it will not be invoked during minimization.

it makes no sense, anyway. minimization is *always* a 0 Kelvin
operation where kinetic energy and atom velocities are not considered.
for a system at finite temperature you always have an "ensemble" of
equivalent states and thus can only determine "ensemble averages".
there is no such thing as "a minimum".

i suggest you spend some quality time with your favorite statistical
mechanics and molecular dynamics text books and revisit the parts
about minimization and statistical mechanical ensembles.

axel.