sbessel.hpp

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// Copyright (c) 2013-2018 Anton Kozhevnikov, Thomas Schulthess
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/** \file sbessel.hpp
 *
 *  \brief Contains implementation of sirius::Spherical_Bessel_functions class.
 */
 
#ifndef __SBESSEL_HPP__
#define __SBESSEL_HPP__
 
#include <vector>
#include "radial/spline.hpp"
#include "radial/radial_grid.hpp"
 
namespace sirius {
 
namespace sf {
 
/// Spherical Bessel functions \f$ j_{\ell}(q x) \f$ up to lmax.
class Spherical_Bessel_functions
{
  private:
    double q_{0};
 
    Radial_grid<double> const* rgrid_{nullptr};
 
    std::vector<Spline<double>> sbessel_;
 
  public:
    Spherical_Bessel_functions() {}
 
    Spherical_Bessel_functions(int lmax__, Radial_grid<double> const& rgrid__, double q__);
 
    static void sbessel(int lmax__, double t__, double* jl__);
 
    static void sbessel_deriv_q(int lmax__, double q__, double x__, double* jl_dq__);
 
    Spline<double> const& operator[](int l__) const;
 
    /// Derivative of Bessel function with respect to q.
    /** \f[
        \frac{\partial j_{\ell}(q x)}{\partial q} = \frac{\ell}{q} j_{\ell}(q x) - x j_{\ell+1}(q x)
        \f]
     */
    Spline<double> deriv_q(int l__);
 
};
 
} // namespace sf
 
}; // namespace sirius
 
#endif