ChargeSeparationParameter.h

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#ifndef SPARROW_CHARGESEPARATIONPARAMETER_H
#define SPARROW_CHARGESEPARATIONPARAMETER_H

#include "Sparrow/Implementations/Nddo/Utils/IntegralsEvaluationUtils/multipoleTypes.h"
#include <array>

namespace Scine {
namespace Sparrow {
namespace nddo {
namespace multipole {

class ChargeSeparationParameter {
 public:
  ChargeSeparationParameter();

  void computeFromExponents(unsigned int ns, unsigned int np, double zs, double zp);
  void computeFromExponents(unsigned int ns, unsigned int np, unsigned int nd, double zs, double zp, double zd);
  void set(MultipolePair type, double value);
  double get(MultipolePair type) const;

 private:
  long long factorial(long long n) const;
  double A(unsigned int n1, unsigned int n2, double z1, double z2, int L) const;
  std::array<double, 5> D_;
};

inline void ChargeSeparationParameter::set(nddo::multipole::MultipolePair type, double value) {
  using Underlying = std::underlying_type<nddo::multipole::MultipolePair>::type;
  D_[static_cast<Underlying>(type)] = value;
}

inline double ChargeSeparationParameter::get(nddo::multipole::MultipolePair type) const {
  using Underlying = std::underlying_type<nddo::multipole::MultipolePair>::type;
  return D_[static_cast<Underlying>(type)];
}

} // namespace multipole
} // namespace nddo
} // namespace Sparrow
} // namespace Scine
#endif // SPARROW_CHARGESEPARATIONPARAMETER_H