SPRING_K
SPRING_K = [real (array)]
Description: Force constant for harmonic bias potential.
The parameter SPRING_K defines force constants ([math]\displaystyle{ \kappa_{\mu} }[/math]) for the harmonic bias of the following 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.
The units of [math]\displaystyle{ \kappa_{\mu} }[/math] are [math]\displaystyle{ eV/uc }[/math] where [math]\displaystyle{ uc }[/math] units of 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_K must be equal to [math]\displaystyle{ M_8 }[/math], otherwise the calculation terminates with an error message.
Related tags and articles
SPRING_R0, SPRING_V0, ICONST, Biased molecular dynamics