TEBEG: Difference between revisions
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{{TAGDEF|TEBEG|[real]|0}} | {{TAGDEF|TEBEG|[real]|0}} | ||
Description: {{TAG|TEBEG}} sets the | Description: {{TAG|TEBEG}} sets the starting temperature (in K) for an ab-initio molecular dynamics run ({{TAG|IBRION}}=0) and other routines (e.g. {{TAG|Electron-phonon interactions from Monte-Carlo sampling}}). | ||
---- | ---- | ||
If no initial velocities are supplied on the {{FILE|POSCAR}} file, the velocities are set randomly according to a Maxwell-Boltzmann distribution at the initial temperature {{TAG|TEBEG}}. Velocities are only used for molecular dynamics ({{TAG|IBRION}}=0). | If no initial velocities are supplied on the {{FILE|POSCAR}} file, the velocities are set randomly according to a Maxwell-Boltzmann distribution at the initial temperature {{TAG|TEBEG}}. Velocities are only used for molecular dynamics ({{TAG|IBRION}}=0). | ||
'''Mind''': VASP defines the temperature as | '''Mind''': If {{TAG|MDALGO}}>0 is used VASP defines the temperature as | ||
:<math> | :<math> | ||
T= \frac{1}{ k_B T 3 (N_{\rm ions}-N_{\rm constraints}) | T= \frac{1}{ k_B T 3 (N_{\rm ions}-N_{\rm constraints})} \sum\limits_{n}^{N_{\rm ions}} M_n | \vec v_n |^2. | ||
</math> | </math> | ||
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*{{TAG|Nose-Hoover thermostat}}: | *{{TAG|Nose-Hoover thermostat}}: | ||
In this thermostat the number of degrees of freedom including constraines are already acounted for in the potential energy term. In this this method the center of mass is conserved. This lowers the degrees of freedom by one which is also taken into account in the {{TAG|OUTCAR}} file | In this thermostat the number of degrees of freedom including constraines are already acounted for in the potential energy term. In this this method the center of mass is conserved. This lowers the degrees of freedom by one which is also taken into account in the {{TAG|OUTCAR}} file. | ||
*{{TAG|Andersen thermostat}}: | *{{TAG|Andersen thermostat}}: | ||
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*{{TAG|Langevin thermostat}}: | *{{TAG|Langevin thermostat}}: | ||
As for the {{TAG|Nose-Hoover thermostat}} in this thermostat the number of degrees of freedom including constraines are already acounted for. The center | As for the {{TAG|Nose-Hoover thermostat}} and {{TAG|Andersen thermostat}} in this thermostat the number of degrees of freedom including constraines are already acounted for. The center of mass is not conserved in this method, hence this method has 3 degrees of freedom more than the {{TAG|Nose-Hoover thermostat}} and {{TAG|Andersen thermostat}}. | ||
== Related tags and articles == | |||
== Related | |||
{{TAG|TEEND}}, | {{TAG|TEEND}}, | ||
{{TAG|IBRION}}, | {{TAG|IBRION}}, | ||
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---- | ---- | ||
[[Category:INCAR]][[Category:Molecular | [[Category:INCAR tag]][[Category:Molecular dynamics]] | ||
Latest revision as of 12:22, 7 September 2022
TEBEG = [real]
Default: TEBEG = 0
Description: TEBEG sets the starting temperature (in K) for an ab-initio molecular dynamics run (IBRION=0) and other routines (e.g. Electron-phonon interactions from Monte-Carlo sampling).
If no initial velocities are supplied on the POSCAR file, the velocities are set randomly according to a Maxwell-Boltzmann distribution at the initial temperature TEBEG. Velocities are only used for molecular dynamics (IBRION=0).
Mind: If MDALGO>0 is used VASP defines the temperature as
This temperature ist written to the OUTCAR file. Depending on the type of thermostat this temperature has to be rescaled to obtain the real simulation temperature.
In this thermostat the number of degrees of freedom including constraines are already acounted for in the potential energy term. In this this method the center of mass is conserved. This lowers the degrees of freedom by one which is also taken into account in the OUTCAR file.
Same as for Nose-Hoover thermostat.
As for the Nose-Hoover thermostat and Andersen thermostat in this thermostat the number of degrees of freedom including constraines are already acounted for. The center of mass is not conserved in this method, hence this method has 3 degrees of freedom more than the Nose-Hoover thermostat and Andersen thermostat.