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# Difference between revisions of "SCALEE"

SCALEE = [real]
Default: SCALEE = 1

Description: This tag specifies the scaling constant of the energies and forces.

In thermodynamic integration the free energy difference between two systems is defined as

${\displaystyle \Delta F=\int \limits _{0}^{1}d\lambda \langle U_{1}-U_{0}\rangle }$

where

For thermodynamic integration this parameter controls the coupling parameter ${\displaystyle \lambda }$.

This parameter is only used if SCALEE${\displaystyle \neq }$1.

Usually the thermodynamic integration is carried out from the ideal gas to the liquid state.

If the file DYNMATFULL exists in the calculation directory (from a previous calculation using PHON_NSTRUCT=-1) and SCALEE${\displaystyle \neq }$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

${\displaystyle H_{\lambda }=(1-\lambda )H_{\mathrm {harmonic} }+\lambda H_{\mathrm {abinitio} }.}$