[Pw_forum] Temperature and pressure control in CP dymics of example 18
lily_physics at yahoo.com.sg
Mon Aug 2 14:01:28 CEST 2010
I would like to study MD with NPT ensemble. I am learning example 18 in QE 4.2.1 which uses cp.x to perform molecular dynamics simulation of SiO2.
For the vc-cp simulation, input file specify tempw=300 and press=1.0. However, the Averaged Physical Quantities
accomulated this run
ekinc : 0.00001 0.00001 (AU)
ekin : 94.60238 94.60238 (AU)
epot : -343.05127 -343.05127 (AU)
total energy : -211.98234 -211.98234 (AU)
temperature : 0.75835 0.75835 (K )
enthalpy : -211.93045 -211.93045 (AU)
econs : -211.93020 -211.93020 (AU)
pressure : -2.19645 -2.19645 (Gpa)
volume : 1526.61474 1526.61474 (AU)
Why the averaged temperature and pressure in the output file are far away from the target value set in the input?
One more question, what is the purpose of using cp, cp-restart, vc-cp, and vc-cp-restart together? Is this a routine to study MD, i.e. combing these four? In other words, could we just get the vc-cp part for investigating NPT ensemble?
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