dispersion.hpp

#pragma once
 
#include "excgrid/error.hpp"
#include "excgrid/geometry.hpp"
 
#include <array>
#include <cstddef>
#include <string_view>
#include <vector>
 
namespace excgrid {


struct D3Parameters {
    double s6 = 1.0; 
    double s8 = 1.0; 
    double rs6 = 1.0; 
    double alpha6 = 14.0; 
    double rs8 = 1.0; 
    double alpha8 = 16.0; 
};

Result<D3Parameters> D3Preset(std::string_view name);

Result<double> GrimmeD3Energy(const Geometry& geometry, const D3Parameters& parameters);

struct D3Result {
    double energy = 0.0; 
    std::vector<std::array<double, 3>> gradient; 
};

Result<D3Result> GrimmeD3(const Geometry& geometry, const D3Parameters& parameters);
 
} // namespace excgrid