Dear Lammps users,
I simulated SPC/E water with pppm in NPT with the last major release (21 May 2008 C++ version).
Temperature and pressure are set to 300K, and 1 atm, respectively. However, when the simulated system
seems to be equilibrated well for over100 ps (timestep = 1fs), there is a problem occuring
“Error: Out of range atoms -cannot comput pppm” as follows:
---------------- Step 100400 ----- CPU = 73790.7981 (sec) ----------------
TotEng = -44757.2104 KinEng = 8704.7139 Temp = 304.2245
PotEng = -53461.9244 E_bond = 0.0000 E_angle = 0.0000
E_dihed = 0.0000 E_impro = 0.0000 E_vdwl = 10448.7418
E_coul = 184310.0114 E_long = -248220.6776 Press = 148.1073
Volume = 145143.9950
---------------- Step 100450 ----- CPU = 73827.3053 (sec) ----------------
TotEng = -44683.6312 KinEng = 8680.9545 Temp = 303.3941
PotEng = -53364.5858 E_bond = 0.0000 E_angle = 0.0000
E_dihed = 0.0000 E_impro = 0.0000 E_vdwl = 10368.2562
E_coul = 184483.8674 E_long = -248216.7094 Press = 83.9992
Volume = 145435.2436
ERROR: Out of range atoms - cannot compute PPPM
I noted that the average thermo properites obtained from the 100ps (with an equilibration of
10 pico seconds ) are pretty much close to water (denstiy:0.986g/cc, T = 300.01K, P = 5.02 atm).
I also found the former respondences about the issue by Steve. However, these situations
where the problem occured seem different from the case presented here, in which I tend to
belive that the simulated system has been equilibrated.
Additionally, Is the PPPM used with NVT more stable than with NPT ?
Attached is my input and data file for 4800 molecules.
Kindly check my input file. Am I missing some command here?
Thanks
in.h2o (866 Bytes)
Water.date (826 KB)