/*   []----------------------------------------[]
      |             LennardJones.h             |
     []----------------------------------------[]
      |                                        |
      |   AUTHOR:    MFSomers 2005.            |
      |   USE:       Defines a Lennard-Jones   |
      |              type interaction...       |
      |                                        |
     []----------------------------------------[]
*/

// Copyright (C) 2005 M.F. Somers, Theoretical Chemistry Department, Leiden University
//
// This is free software; you can redistribute it and/or modify it under the terms of
// the GNU Lesser General Public License as published by the Free Software Foundation.
//
// http://www.gnu.org/licenses/lgpl.txt

#if !defined(__LENNARDJONES_INCLUDED__)

#define __LENNARDJONES_INCLUDED__

#include "Global.h"
#include "Vector.h"
#include "Constants.h"
#include "ClassicalDynamics.h"
#include "PointPair.h"

/* --------------------------------------------------------- */
/* Defines a LennardJones pointpair interaction between particles */

class   LennardJonesInteraction;
typedef LennardJonesInteraction *LennardJonesInteractionPointer;

class LennardJonesInteraction : public PointPairInteraction
                         {
		 	  public:
			     
			  inline LennardJonesInteraction( double TheEpsilon, double TheR, unsigned int TheId = GET_NEW_ID, Vector *UsePeriodicBox = NULL ) : PointPairInteraction( TheId, UsePeriodicBox )
			  {
                           Epsilon = TheEpsilon;
			   R = TheR;
			   Type = ALennardJonesInteraction;
			  }
			  inline LennardJonesInteraction( LennardJonesInteraction& I ) : PointPairInteraction( I )
			  {
		           Epsilon = I.Epsilon;
			   R = I.R;
			  }

          	          virtual LennardJonesInteraction& operator=( LennardJonesInteraction& I )
			  {
			   if( &I == &(*this) ) return( (*this) );
			   PointPairInteraction::operator=( I );
		           Epsilon = I.Epsilon;
			   R = I.R;		   
			   return( (*this) );
			  } 			    
		          virtual LennardJonesInteractionPointer Clone()
		          {
		           return( new LennardJonesInteraction( (*this) ) );
		          }
		          virtual LennardJonesInteractionPointer Create( double TheEpsilon = 1.0, double TheR = 1.0, unsigned int TheId = GET_NEW_ID, Vector *UsePeriodicBox = NULL )
		          {
		           return( new LennardJonesInteraction( TheEpsilon, TheR, TheId, UsePeriodicBox ) );
		          }
				    
			  virtual double PointPairPotential( Particle& P1, Particle& P2 );
			  virtual Vector PointPairForce( Particle& P1, Particle& P2 );
			  
			  double Epsilon, R;       /* V(r) = Epsilon * { (R/r)^12 - 2 * (R/r)^6 } */
			 };
			   
/* --------------------------------------------------------- */

#endif