DHENERGY

This is part of the colvar module |

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 [39]. Notice that the value of the DHENERGY is returned in plumed units (see UNITS).

If GROUPB is empty, it will sum the N*(N-1)/2 pairs in GROUPA. This avoids computing twice permuted indexes (e.g. pair (i,j) and (j,i)) thus running at twice the speed.

Notice that if there are common atoms between GROUPA and GROUPB their interaction is discarded.

- Examples

Click on the labels of the actions for more information on what each action computes

# this is printing the electrostatic interaction between two groups of atomsdh:DHENERGYGROUPA=1-10First list of atoms.GROUPB=11-20Second list of atoms (if empty, N*(N-1)/2 pairs in GROUPA are counted).EPSILON=80.0compulsory keyword ( default=80.0 )Dielectric constant of solventI=0.1compulsory keyword ( default=1.0 )Ionic strength (M)TEMP=300.0 PRINTcompulsory keyword ( default=300.0 )Simulation temperature (K)ARG=compulsory keywordthe labels of the values that you would like to print to the filedh

- Glossary of keywords and components

- Description of components

By default the value of the calculated quantity can be referenced elsewhere in the input file by using the label of the action. Alternatively this Action can be used to calculate the following quantities by employing the keywords listed below. These quantities can be referenced elsewhere in the input by using this Action's label followed by a dot and the name of the quantity required from the list below.

Quantity | Description |

.#!value | the value of the DHENERGY |

- The atoms involved can be specified using

GROUPA | First list of atoms. For more information on how to specify lists of atoms see Groups and Virtual Atoms |

GROUPB | Second list of atoms (if empty, N*(N-1)/2 pairs in GROUPA are counted). For more information on how to specify lists of atoms see Groups and Virtual 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 neighbor list to speed up the calculation |

NL_CUTOFF | The cutoff for the neighbor list |

NL_STRIDE | The frequency with which we are updating the atoms in the neighbor list |