[Pw_forum] heat and quench using BO MD

[Stefano de Gironcoli]

if you are performing a microcanonical MD simulation the total energy is 
conserved but not the kinetic energy that is related to the 
instantaneous temperature.
kinetic energy fluctuates around an average value. the larger the number 
of atoms the smaller should be temperature fluctuation.

stefano

On 02/19/2013 08:12 PM, dev pe wrote:
> Dear QE users
> I am trying to model amorphous Si using heat-and-quench by BO molecular
> dynamics (based on example3). My starting temperature is 1600K. But, In my
> output file, after every step, I see a different instantaneous temperature
> printed. Why is that so? Am I missing any input parameter? My input file is
> as given below:
>
>   &control
>      calculation='md'
>      restart_mode='from_scratch',
>      prefix = 'Si'
>      pseudo_dir = '/home/deva/espresso-5.0.1/pseudo/',
>      outdir='./',
>      dt=20,
>      nstep=60,
>      disk_io='high'
>   /
>   &system
>      ibrav= 1, celldm(1)=10.18, nat=  8, ntyp= 1,
>      ecutwfc = 20.0, nosym=.true.
>   /
>   &electrons
>      conv_thr =  1.0d-8,
>      mixing_beta = 0.7
>   /
>   &ions
>      ion_dynamics='verlet'
>      pot_extrapolation='second-order'
>      wfc_extrapolation='second-order'
>      ion_temperature='reduce-T'
>      tempw=1600.D0
>      delta_t=-400.D0
>      nraise=20
>   /
> ATOMIC_SPECIES
>   Si  28.086  Si.pz-vbc.UPF
> ATOMIC_POSITIONS
>   Si -0.123 -0.123 -0.123
>   Si  0.377  0.377 -0.123
>   Si  0.377 -0.123  0.377
>   Si -0.123  0.377  0.377
>   Si  0.123  0.123  0.123
>   Si  0.623  0.623  0.123
>   Si  0.623  0.123  0.623
>   Si  0.123  0.623  0.623
> K_POINTS {automatic}
>   1 1 1 0 0 0
>
> Thanks in advance
> Devan
> PhD student
> UMD
> College Park
>
>
>
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