[lammps-users] Initial temperature jump with Nose-Hoover integration

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1

Hi all,
I’m a little confused about the origin of a large jump in temperature that I’m seeing in the first few timesteps when I use Nose-Hoover npt or nvt integration and the velocity command with the create style on a box of 6x6x6 cristobalite unit cells. I’m wondering if maybe there’s a problem with using the combination of the two commands–has anyone had similar problems before?

Here’s the thermodynamic output for the first ten timesteps of one such run:
Step Temp E_pair E_mol TotEng Press
0 1500 -99875.74 0 -98870.807 218812.86
1 1374.7166 -99787.27 0 -98866.271 219516.46
2 1094.2499 -99589.908 0 -98856.81 220141.61
3 856.59495 -99425.022 0 -98851.142 218085.17
4 782.287 -99377.751 0 -98853.654 212458.19
5 822.2138 -99411.1 0 -98860.253 204860.42
6 841.22175 -99426.925 0 -98863.344 198271.17
7 773.43919 -99378.51 0 -98860.34 194490.07
8 681.07121 -99311.59 0 -98855.302 192536.78
9 674.26431 -99305.522 0 -98853.795 189882.33
10 792.45275 -99388.393 0 -98857.485 184815.86

and here’s the corresponding input script:

2

If you start with a perfect lattice, the temperature will
drop when you start a run b/c of equipartitioning
the potential and kinetic energy. This has nothing to
do with Nose/Hoover or thermostatting.

Steve