Temperature during molecular dynamics

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neo
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Temperature during molecular dynamics

#1 Post by neo » Sun Apr 25, 2010 11:14 am

hello everybody

i am doing simulated annealing of silicon clusters using VASP. In the OUTCAR file there is a warning that temperature is equal to (2*EKIN)/(degrees of freedom). I am heating my sample upto 1400K . i wanna to know what is the actual temperature. It is what i have specified in INCAR file or given by expression above
The INCAR file and warning messages are given below

SYSTEM=si5
Startparameter for this run:
NWRITE=1
ISTART=0
ISMEAR=0
ICHARGE=2
GGA=91
LCHARGE=.FALSE.
Electronic relaxation:
ENCUT=250
PREC=low
BMIX=2
MAXMIX=50
Ionic ralaxation:
IALGO=48
Parallezation flags:
NPAR=1
LPLANE=.True.
NSW=1420
ISIF=3
NBLOCK=1
SMASS=-1
IBRION=0
POTIM=1
TEIN=0
TEBEG=0
TEEND=1420
ISYM=0


and the warning message is

-----------------------------------------------------------------------------
| |
| W W AA RRRRR N N II N N GGGG !!! |
| W W A A R R NN N II NN N G G !!! |
| W W A A R R N N N II N N N G !!! |
| W WW W AAAAAA RRRRR N N N II N N N G GGG ! |
| WW WW A A R R N NN II N NN G G |
| W W A A R R N N II N N GGGG !!! |
| |
| VASP found 12 degrees of freedom |
| the temperature will equal 2*E(kin)/ (degrees of freedom) |
| this differs from previous releases, where T was 2*E(kin)/(3 NIONS). |
| The new definition is more consistent |
| |
-----------------------------------------------------------------------------

Value of EKIN coming out to be

ENERGIE OF THE ELECTRON-ION-THERMOSTAT SYSTEM (eV)
---------------------------------------------------
% ion-electron TOTEN = -15.673754 see above
kinetic Energy EKIN = 0.734201 (temperature 1420.00 K)
nose potential ES = 0.000000
nose kinetic EPS = 0.000000
---------------------------------------------------
total energy ETOTAL = -14.939553 eV

and temperature according to warning message is coming to be 0.1223. is this the actual temperature....

please help

thanks in advance
Last edited by neo on Sun Apr 25, 2010 11:14 am, edited 1 time in total.

forsdan
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Temperature during molecular dynamics

#2 Post by forsdan » Sun Apr 25, 2010 12:12 pm

The value 0.1223 is given in eV, equivalent to the product k*T, where k is Boltzmanns constant. The corresponding temperature T is then 1420 K as stated in the output.

/Dan

<span class='smallblacktext'>[ Edited Sun Apr 25 2010, 02:13PM ]</span>
Last edited by forsdan on Sun Apr 25, 2010 12:12 pm, edited 1 time in total.

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neo
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Temperature during molecular dynamics

#3 Post by neo » Sun Apr 25, 2010 5:02 pm

thanks dear
Last edited by neo on Sun Apr 25, 2010 5:02 pm, edited 1 time in total.

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