ML LCOUPLE

ML_FF_LCOUPLE_MB = [logical]
Default: ML_FF_LCOUPLE_MB = .FALSE. 

Description: This tag specifies whether coupling parameters are used for the calculation of chemical potentials is used or not within the machine learning force field method.

---

In thermodynamic integration a coupling parameter $\lambda$ is introduced to the Hamiltonian to smoothly switch between a "non-interacting" reference state and a "fully-interacting" state. The change of the free energy along this path is written as

$\delta \mu =\int \limits _{0}^{1}\langle {\frac {dH(\lambda )}{d\lambda }}\rangle _{\lambda }d\lambda .$

Using machine learning force fields the Hamiltonian can be written as

$H(\lambda )=\sum \limits _{i=1}^{N_{a}}{\frac {|\mathbf {p} _{i}|^{2}}{2m_{i}}}+\sum \limits _{i\notin M}U_{i}(\lambda )+\lambda \sum \limits _{i\in M}U_{i}(\lambda )+\sum \limits _{i}^{N_{a}}U_{i,\mathbf {atom} }.$

where $N_{a}$ denotes the number of atoms and $U_{i,\mathbf {atom} }$ is an atomic reference energy for a single non interacting atom. The first term in the equation describes the potential energy and the second and third term describe the potential energy of an atom $i$. The index $M$ denotes the atoms whose interaction is controlled by a coupling parameter. Further details on the implementation can be found in reference .

Related Tags and Sections

ML_FF_LMLFF, ML_FF_NATOM_COUPLED_MB, ML_FF_ICOUPLE_MB, ML_FF_RCOUPLE_MB

Examples that use this tag

---