DHENERGY

Calculate Debye-Huckel interaction energy among GROUPA and GROUPB.

This variable calculates the electrostatic interaction among GROUPA and GROUPB using a Debye-Huckel approximation defined as

\[ \frac{1}{4\pi\epsilon_r\epsilon_0} \sum_{i\in A} \sum_{j \in B} q_i q_j \frac{e^{-\kappa |{\bf r}_{ij}|}}{|{\bf r}_{ij}|} \]

This collective variable can be used to analyze or induce electrostatically driven reactions [do13jctc.] The two atom groups should be disjointed. Notice that the value of the DHENERGY is returned in plumed units (see UNITS).

The atoms involved can be specified using

GROUPA	First list of atoms
GROUPB	Second list of atoms

Compulsory keywords

I	( default=1.0 ) Ionic strength (M)
TEMP	( default=300.0 ) Simulation temperature (K)
EPSILON	( default=80.0 ) Dielectric constant of solvent

Options

NUMERICAL_DERIVATIVES	( default=off ) calculate the derivatives for these quantities numerically
NOPBC	( default=off ) ignore the periodic boundary conditions when calculating distances
SERIAL	( default=off ) Perform the calculation in serial - for debug purpose
PAIR	( default=off ) Pair only 1st element of the 1st group with 1st element in the second, etc
NLIST	( default=off ) Use a neighbour list to speed up the calculation

NL_CUTOFF	The cutoff for the neighbour list
NL_STRIDE	The frequency with which we are updating the atoms in the neighbour list

Examples

# this is printing the electrostatic interaction between two groups of atoms
dh: DHENERGY GROUPA=1-10 GROUPB=11-20 EPSILON=80.0 I=0.1 TEMP=300.0
PRINT ARG=dh

(see also PRINT)