SPRING V0

SPRING_V0 = [real (array)] 

Default: SPRING_V0

= 0

for all coordinates with status=8 in ICONST.

Description: Rate at which the bias potential is shifted in $uc/fs$.

---

Consider the bias potential for a molecular-dynamics (MD) run of the form:

$\tilde{V}(\xi_1,\dots,\xi_{M_8}) = \sum_{\mu=1}^{M_8}\frac{1}{2}\kappa_{\mu} (\xi_{\mu}(q)-\xi_{0\mu})^2, \;$

where the sum runs over all ($M_8$) coordinates the potential acts upon ($\xi_{\mu}(q)$). The coordinates are defined in the ICONST file by setting the status=8. Optionally, the position of minimum ($\xi_{0\mu}$) can be shifted at a constant rate $\dot{\xi}_{\mu}$ every MD step, i.e.,

$\xi_{0\mu}(t+\Delta t) = \xi_{0\mu}(t) + \dot{\xi}_{\mu}(q)\Delta t, \;$

where $\Delta t$ is the time step used in MD (POTIM). The rate $\dot{\xi}_{\mu}$ can be defined via the parameter SPRING_V0 and its units are $uc/fs$, where $uc$ corresponds to the units of the coordinate the potential acts upon (e.g., ${\AA}$ for coordinates with flag R, $rad.$ for coordinates with flag A, dimensionless for coordinates with flag W, etc...). The number of items defined via SPRING_V0 must be equal to $M_8$, otherwise the calculation terminates with an error message.

Related tags and articles

SPRING_K, SPRING_R0, ICONST, Biased molecular dynamics

---