SCALEE: Difference between revisions

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A detailed description of calculations using thermodynamic integration within VASP is given in reference {{cite|dorner:PRL:2018}} ('''caution''': the tag ''ISPECIAL''=0 used in that reference is not valid anymore, instead the tag {{TAG|PHON_NSTRUCT}}=-1 is used).
The tag {{TAG|SCALEE}} sets the coupling parameter <math>\lambda</math> and hence controls the Hamiltonian of the calculation.
By default {{TAG|SCALEE}}=1 and the scaling of the energies and forces via the coupling constant is internally skipped in the code. To enable the scaling {{TAG|SCALEE}}<math>\ne</math>1 has to be specified.


More information using this tag is given [[Thermodynamic integration calculations|here]].


In thermodynamic integration the free energy difference between two systems is defined asthe
== Related tags and articles ==
<math> \Delta F = \int\limits_{0}^{1} d\lambda \langle U_{1}(\lambda) - U_{0}(\lambda) \rangle </math>.
{{TAG|VCAIMAGES}}, {{TAG|IMAGES}}, {{TAG|NCORE IN IMAGE1}}, {{TAG|PHON_NSTRUCT}}, {{TAG|IBRION}}
 
Here <math>U_{1}(\lambda)</math> and <math>U_{0}(\lambda)</math> describe the potential energies of a fully-interacting and a non-interacting reference system, respectively. The interaction of the constituents within the system is controlled via the coupling parameter <math>\lambda</math>. The {{TAG|SCALEE}} sets the value for the coupling constant.
 
By default {{TAG|SCALEE}}=1 and scaling of the energies and forces via the coupling constant is carried out. To enable the scaling {{TAG|SCALEE}}<1 has to be specified.
 
Two possible options are available for the reference system:
 
*Ideal gas:
Usually the thermodynamic integration is carried out from the ideal gas to the liquid state.
 
*Harmonic solid
If the file {{TAG|DYNMATFULL}} exists  in the calculation directory (from a previous calculation using {{TAG|PHON_NSTRUCT}}=-1) and {{TAG|SCALEE}}<math>\ne</math>1, the second order Hessian matrix is added to the force and thermodynamic integration from a harmonic model to a fully interacting system is carried out. Here the Hamiltonian for a certain integration point along the thermodynamic integration pathway is given as
 
<math>H_{\lambda} = (1-\lambda) H_{\mathrm{harmonic}} + \lambda H_{\mathrm{ab initio}}. </math>
== Related Tags and Sections ==
{{TAG|VCAIMAGES}}, {{TAG|IMAGES}}, {{TAG|NCORE IN IMAGE1}}, {{TAG|PHON_NSTRUCT}}


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[[Category:INCAR tag]][[Category:Advanced molecular-dynamics sampling]]
[[Category:INCAR]][[Category:Molecular Dynamics]][[Category:Thermodynamic integration]]

Latest revision as of 14:05, 16 October 2024

SCALEE = [real]
Default: SCALEE = 1 

Description: This tag specifies the coupling parameter of the energies and forces between a fully interacting system and a reference system.


The tag SCALEE sets the coupling parameter and hence controls the Hamiltonian of the calculation. By default SCALEE=1 and the scaling of the energies and forces via the coupling constant is internally skipped in the code. To enable the scaling SCALEE1 has to be specified.

More information using this tag is given here.

Related tags and articles

VCAIMAGES, IMAGES, NCORE IN IMAGE1, PHON_NSTRUCT, IBRION