[QE-users] CP simulation constant of motion increases on thermostatting of electrons

[Rashid Rafeek V Valappil]

Dear all,

We are running NPT simulations on an 80 atom cell. The simulations have
been set up with 'nose' thermostat for ions and the parrinello rahman 'pr'
barostat. The simulations were running fine, but there was a slow increase
in the fictitious kinetic energy 'ekincw' of the electrons. Therefore, the
electronic thermostat was used to control this by setting
`electron_temperature = 'nose'`. But when this was done, the constant of
motion 'econt' which was constant started increasing. The econt values
which had been constant (changes only occurring in the range of 10e-4 a.u)
until the application of electronic thermostat started increasing at a rate
greater than 0.05 a.u per ps.

Is the constant of motion not a constant for electronic thermostat? or does
this imply a discrepancy in the calculation? If so, what would cause this
behaviour?

Any information regarding this will be helpful. The relevant inputs are
given below:

---------------------------------------------------
&electrons
    electron_dynamics = 'verlet',
    emass = 200.d0,
    emass_cutoff = 1.d0,
    electron_velocities = 'default',
    electron_maxstep = 2000,
    conv_thr = 1.0D-10,
    electron_temperature = 'nose',
    ekincw = 0.0125
    fnosee = 150
/
&ions
    ion_dynamics = 'verlet',
    ion_temperature = 'nose',
    tempw= 300.0,
    fnosep = 55.0,
    ion_velocities = 'default',
    ion_positions = 'default',
/
&cell
    cell_dynamics = 'pr',
    cell_parameters = 'default'
    cell_velocities = 'default'
    press = 300.0,
/
--------------------------------------------------------------

Rashid Rafeek
Junior Research Fellow
IISER Bhopal, India
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