CrystalFieldHeatCapacity.cpp

Go to the documentation of this file.

// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2018 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#include "MantidCurveFitting/Functions/CrystalFieldHeatCapacity.h"
#include "MantidAPI/FunctionDomain.h"
#include "MantidAPI/FunctionDomain1D.h"
#include "MantidAPI/FunctionFactory.h"
#include "MantidAPI/FunctionValues.h"
#include "MantidAPI/IFunction1D.h"
#include "MantidAPI/Jacobian.h"
#include "MantidCurveFitting/EigenFortranDefs.h"
#include "MantidCurveFitting/Functions/CrystalFieldPeaksBase.h"
#include "MantidKernel/Exception.h"
#include "MantidKernel/PhysicalConstants.h"
#include <cmath>
 
namespace Mantid::CurveFitting::Functions {
 
namespace {
 
// Does the actual calculation of the heat capacity
void calculate(double *out, const double *xValues, const size_t nData, const DoubleFortranVector &en) {
  const double k_B = PhysicalConstants::BoltzmannConstant; // in meV/K
  // Want output in J/K/mol
  const double convfact = PhysicalConstants::N_A * PhysicalConstants::meV;
  int nlevels = en.len();
  for (size_t iT = 0; iT < nData; iT++) {
    double Z = 0.;
    double U = 0.;
    double U2 = 0.;
    const double beta = 1 / (k_B * xValues[iT]);
    // Using fortran indexing...
    for (auto iE = 1; iE <= nlevels; iE++) {
      double expfact = exp(-beta * en(iE));
      Z += expfact;
      U += en(iE) * expfact;
      U2 += en(iE) * en(iE) * expfact;
    }
    U /= Z;
    U2 /= Z;
    out[iT] = ((U2 - U * U) / (k_B * xValues[iT] * xValues[iT])) * convfact;
  }
}
} // namespace
 
CrystalFieldHeatCapacityBase::CrystalFieldHeatCapacityBase() : API::IFunction1D() {
  declareAttribute("ScaleFactor", Attribute(1.0));
}
 
void CrystalFieldHeatCapacityBase::function1D(double *out, const double *xValues, const size_t nData) const {
  // Use stored values
  calculate(out, xValues, nData, m_en);
  auto fact = getAttribute("ScaleFactor").asDouble();
  if (fact != 1.0) {
    for (size_t i = 0; i < nData; i++) {
      out[i] *= fact;
    }
  }
}
 
DECLARE_FUNCTION(CrystalFieldHeatCapacity)
 
CrystalFieldHeatCapacity::CrystalFieldHeatCapacity()
    : CrystalFieldPeaksBase(), CrystalFieldHeatCapacityBase(), m_setDirect(false) {}
 
// Sets the eigenvectors / values directly
void CrystalFieldHeatCapacity::setEnergy(const DoubleFortranVector &en) {
  m_setDirect = true;
  m_en = en;
}
 
void CrystalFieldHeatCapacity::function1D(double *out, const double *xValues, const size_t nData) const {
  if (!m_setDirect) {
    ComplexFortranMatrix wf;
    int nre = 0;
    calculateEigenSystem(m_en, wf, nre);
  }
  CrystalFieldHeatCapacityBase::function1D(out, xValues, nData);
}
 
CrystalFieldHeatCapacityCalculation::CrystalFieldHeatCapacityCalculation()
    : API::ParamFunction(), CrystalFieldHeatCapacityBase() {}
 
// Sets the eigenvectors / values directly
void CrystalFieldHeatCapacityCalculation::setEnergy(const DoubleFortranVector &en) { m_en = en; }
 
} // namespace Mantid::CurveFitting::Functions