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| All tags and articles that deal with Interface Pinning calculations are members of this category.
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| == Theoretical Background ==
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| Interface Pinning is a method for finding melting points from an MD simulation of a system where the liquid and the solid phase are in contact. To prevent melting or freezing at constant pressure and constant temperature, a bias potential applies a penalty energy for deviations from the desired two phase system.
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| The Steinhardt-Nelson Q 6 {\displaystyle Q_{6}} order parameter is used for discriminating the solid from the liquid phase and the bias potential is given by
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| U bias ( R ) = κ 2 ( Q 6 ( R ) − a ) 2 {\displaystyle U_{{\textrm {bias}}}({\mathbf {R}})={\frac \kappa 2}\left(Q_{6}({\mathbf {R}})-a\right)^{2}}
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| where Q 6 ( R ) {\displaystyle Q_{6}({{\mathbf {R}}})} is the Steinhardt-Nelson Q 6 {\displaystyle Q_{6}} orientational order parameter for the current configuration R {\displaystyle {\mathbf {R}}} and a {\displaystyle a} is the desired value of the order parameter close to the order parameter of the initial two phase configuration.
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| With the bias potential enabled, the system can equilibrate while staying in the two phase configuration. From the difference of the average order parameter ⟨ Q 6 ⟩ {\displaystyle \langle Q_{6}\rangle } in equilibrium and the desired order parameter a {\displaystyle a} one can directly compute the difference of the chemical potential of the solid and the liquid phase:
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| N ( μ solid − μ liquid ) = κ ( Q 6 solid − Q 6 liquid ) ( ⟨ Q 6 ⟩ − a ) {\displaystyle N(\mu _{{\textrm {solid}}}-\mu _{{\textrm {liquid}}})=\kappa (Q_{{6{\textrm {solid}}}}-Q_{{6{\textrm {liquid}}}})(\langle Q_{6}\rangle -a)}
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| where N {\displaystyle N} is the number of atoms in the simulation.
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| == How to ==
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| A comprehensive documentation on interface pinning calculations is given in {{TAG|Interface pinning calculations}}.
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| ----
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| [[The_VASP_Manual|Contents]]
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| [[Category:VASP|Interface Pinning]][[Category:Molecular Dynamics|Molecular Dynamics]]
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Latest revision as of 11:48, 16 October 2024
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