[Pw_forum] Problem in energy conservation in NVE MD using cp.x

[SAKUMA Hiroshi]

Dear all,

I was running the cp.x using the example input files in
a folder of "examples_cp/water-cp" provided by Summer School 2006, Quantum Espresso Lab.
After the wavefunction optimization, I tried a MD run of NVE ensemble using the h2o_mol.in.03.
The total energy (econt) was almost constant until 0.2 ps, 
however it exponentially increased after 0.2 ps.
This is not affected by the choice of time step and fictious mass.

I used the Quantum-espresso 4.0.5 and 4.0.3.

Do you have any idea about this problem?

Thanks,

Hiroshi Sakuma

- 
Department of Earth & Planetary Sciences
Graduate School of Science & Engineering
Tokyo Institute of Technology
2-12-1 Ookayama Meguro-ku Tokyo 1528551
Kawamura Lab.
Tel: +81-3-5734-2617


# h2o_mol.in.03
# Electronic + Ionic Dynamic
# quenching electrons and ions.

&CONTROL
title = ' Water Molecule ',
calculation = 'cp',
restart_mode = 'reset_counters',
ndr = 51,
ndw = 52,
nstep = 5000,
iprint = 5,
isave = 100,
tstress = .FALSE.,
tprnfor = .TRUE.,
dt = 4.0d0,
etot_conv_thr = 1.d-9,
ekin_conv_thr = 1.d-4,
prefix = 'h2o_mol'
/

&SYSTEM
ibrav = 14,
celldm(1) = 10.0, celldm(2) = 1.0, celldm(3) = 1.0,
celldm(4) = 0.0, celldm(5) = 0.0, celldm(6) = 0.0,
nat = 3,
ntyp = 2,
ecutwfc = 70.0,
nr1b = 16, nr2b = 16, nr3b = 16
/

&ELECTRONS
emass = 300.d0,
emass_cutoff = 2.5d0,
orthogonalization = 'ortho',
electron_dynamics = 'verlet',
electron_velocities = 'zero',
electron_temperature = 'not_controlled',
/

&IONS
ion_dynamics = 'verlet',
ion_velocities = 'zero',
ion_temperature = 'not_controlled',
/

ATOMIC_SPECIES
O 16.0d0 O.BLYP.UPF
H 1.00d0 H.fpmd.UPF

ATOMIC_POSITIONS (bohr)
O 5.0099 5.0099 5.0000 0 0 0
H 6.8325 4.7757 4.9999 1 1 1
H 4.7757 6.8325 4.9998 1 1 1