UniformField.hpp

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 * [7] Lamichhane, Newman & Gezelter, J. Chem. Phys. 141, 134110 (2014).
 * [8] Bhattarai, Newman & Gezelter, Phys. Rev. B 99, 094106 (2019).
 */
 
/*! \file perturbations/UniformField.hpp
    \brief Uniform Electric Field perturbation
*/
 
#ifndef PERTURBATIONS_UNIFORMFIELD_HPP
#define PERTURBATIONS_UNIFORMFIELD_HPP
 
#include "brains/ForceModifier.hpp"
#include "brains/SimInfo.hpp"
 
namespace OpenMD {
 
  //! Applies a uniform (vector) electric field to the system
  /*! The field is applied as an external perturbation.  The user specifies
 
  \code{.unparsed}
    uniformField = (a, b, c);
  \endcode
 
    in the .omd file where the values of a, b, and c are in units of
    \f$ V / \AA \f$
 
    The electrostatic potential corresponding to this uniform field is
 
    \f$ \phi(\mathbf{r})  = - a x - b y - c z \f$
 
    which grows unbounded and is not periodic.  For these reasons,
    care should be taken in using a Uniform field with point charges.
 
    The field itself is
 
    \f$ \mathbf{E} = \left( \begin{array}{c} a \\ b \\ c \end{array} \right) \f$
 
   The external field applies a force on charged atoms, \f$ \mathbf{F}
   = C \mathbf{E} \f$.  For dipolar atoms, the field applies both a
   potential, \f$ U = - \mathbf{D} \cdot \mathbf{E} \f$ and a torque,
   \f$ \mathbf{\tau} = \mathbf{D} \times \mathbf{E} \f$.
  */
  class UniformField : public ForceModifier {
  public:
    UniformField(SimInfo* info);
 
  private:
    void modifyForces() override;
    void initialize();
 
    bool initialized;
    bool doUniformField;
    bool doParticlePot;
 
    Globals* simParams;
    Vector3d EF;
  };
}  // namespace OpenMD
 
#endif