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., ${\mathrm {\AA} }$ 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.

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