SPRING V0: Difference between revisions
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Description: Consider the bias potential of the form: | Description: Consider the bias potential of the form: | ||
<math> | <math> | ||
\tilde{V}(\xi_1,\dots,\xi_{M_8}) = \sum_{\mu=1}^{M}\frac{1}{2}\kappa_{\mu} (\xi_{\mu}(q)-\xi_{0\mu})^2 \; | \tilde{V}(\xi_1,\dots,\xi_{M_8}) = \sum_{\mu=1}^{M}\frac{1}{2}\kappa_{\mu} (\xi_{\mu}(q)-\xi_{0\mu})^2 \; | ||
</math> | </math> | ||
where the sum runs over all (<math>M_8</math>) coordinates the potential acts upon (<math>\xi_{\mu}(q)</math>), which are defined in the {{FILE|ICONST}}-file by setting the status to 8. | where the sum runs over all (<math>M_8</math>) coordinates the potential acts upon (<math>\xi_{\mu}(q)</math>), which are defined in the {{FILE|ICONST}}-file by setting the status to 8. | ||
Optionally, the position of minimum (<math>\xi_{0\mu}</math>) can be shifted at a constant rate <math>\dot{\xi}_{\mu}</math> every MD step, i.e. | Optionally, the position of minimum (<math>\xi_{0\mu}</math>) can be shifted at a constant rate <math>\dot{\xi}_{\mu}</math> every MD step, i.e. | ||
<math> | <math> | ||
\xi_{0\mu}(t+\Delta t) = \xi_{0\mu}(t) + \dot{\xi}_{\mu}(q)\Delta t \; | \xi_{0\mu}(t+\Delta t) = \xi_{0\mu}(t) + \dot{\xi}_{\mu}(q)\Delta t \; | ||
</math> | </math> | ||
where <math>\Delta t</math> is the time step used in MD ({{TAG|POTIM}}). | where <math>\Delta t</math> is the time step used in MD ({{TAG|POTIM}}). | ||
The rate <math>\dot{\xi}_{\mu}</math> can be defined via the parameter {{TAG|SPRING_V0}} and its units are <math>uc/fs</math>, where <math>uc</math> corresponds to the units of the coordinate the potential acts upon (e.g., <math>{\AA}</math> for coordinates with <code>flag</code> R, <math>rad.</math> for coordinates with <code>flag</code> A, dimensionless for coordinates with <code>flag</code> W, etc...). | The rate <math>\dot{\xi}_{\mu}</math> can be defined via the parameter {{TAG|SPRING_V0}} and its units are <math>uc/fs</math>, where <math>uc</math> corresponds to the units of the coordinate the potential acts upon (e.g., <math>{\AA}</math> for coordinates with <code>flag</code> R, <math>rad.</math> for coordinates with <code>flag</code> A, dimensionless for coordinates with <code>flag</code> W, etc...). | ||
Revision as of 08:42, 11 April 2023
SPRING_V0 = [real (array)]
Description: Consider the bias potential of the form:
[math]\displaystyle{ \tilde{V}(\xi_1,\dots,\xi_{M_8}) = \sum_{\mu=1}^{M}\frac{1}{2}\kappa_{\mu} (\xi_{\mu}(q)-\xi_{0\mu})^2 \; }[/math]
where the sum runs over all ([math]\displaystyle{ M_8 }[/math]) coordinates the potential acts upon ([math]\displaystyle{ \xi_{\mu}(q) }[/math]), which are defined in the ICONST-file by setting the status to 8. Optionally, the position of minimum ([math]\displaystyle{ \xi_{0\mu} }[/math]) can be shifted at a constant rate [math]\displaystyle{ \dot{\xi}_{\mu} }[/math] every MD step, i.e.
[math]\displaystyle{ \xi_{0\mu}(t+\Delta t) = \xi_{0\mu}(t) + \dot{\xi}_{\mu}(q)\Delta t \; }[/math]
where [math]\displaystyle{ \Delta t }[/math] is the time step used in MD (POTIM).
The rate [math]\displaystyle{ \dot{\xi}_{\mu} }[/math] can be defined via the parameter SPRING_V0 and its units are [math]\displaystyle{ uc/fs }[/math], where [math]\displaystyle{ uc }[/math] corresponds to the units of the coordinate the potential acts upon (e.g., [math]\displaystyle{ {\AA} }[/math] for coordinates with flag R, [math]\displaystyle{ rad. }[/math] for coordinates with flag A, dimensionless for coordinates with flag W, etc...).
The number of items defined via SPRING_V0 must be equal to [math]\displaystyle{ M_8 }[/math], otherwise the calculation terminates with an error message.