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Definition of External Electrostatic Fields

This submenu allows you to calculate first and second numerical derivatives of the energy with respect to an external electric field. The first three options should be clear; 1st and 2nd are logical switches which are turned on and off the usual way (1st or -1st) and delta is the increment for the numerical differentiation, that is, the finite value of the external field, which replaces the (ideally) differential field:

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electrostatic field definition menu
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option       | status | description
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1st          |    F   | numerical 1st derivative dE/dField
2nd          |    F   | numerical 2nd derivative d2E/dField2
delta <real> |        | increment for numerical differentiation
             |        | DEFAULT =    .5000E-02
geofield     |    F   | geometry optimization with external field
man          |    F   | explicit definition of electrostatic field(s)
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geofield gives the possibility to perform a whole geometry optimization under the influence of a finite external field and thus to obtain the (distorted) minimum geometry in this field. To do this, an external electrostatic field must be defined explicitly which can be done using command man. Note that geofield must also be switched on if any properties are to be evaluated in the presence of an electric field. The most prominent example is the calculation of hyperpolarizabilies.

Take Care, due to some inconsistencies in define it is always necessary to switch on the field calculations manually. Therefore edit the control file after having finished your define session and enter on after the entries of fields and geofield.


next up previous contents index
Next: Properties Up: The General Options Menu Previous: Initialization of the Hessian   Contents   Index
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