/usr/include/libint2/chemistry/sto3g_atomic_density.h is in libint2-dev 2.3.0~beta3-2.
This file is owned by root:root, with mode 0o644.
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* This file is a part of Libint.
* Copyright (C) 2004-2016 Edward F. Valeev
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Library General Public License, version 2,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU Library General Public License
* along with this program. If not, see http://www.gnu.org/licenses/.
*
*/
#ifndef INCLUDE_LIBINT2_CHEMISTRY_STO3GATOMICDENSITY_H_
#define INCLUDE_LIBINT2_CHEMISTRY_STO3GATOMICDENSITY_H_
#include <algorithm>
#include <vector>
namespace libint2 {
namespace detail {
/// computes orbital occupation numbers for a subshell of size \c size created
/// by smearing
/// no more than \c ne electrons (corresponds to spherical averaging)
///
/// @param[in,out] occvec occupation vector, increments by \c size on return
/// @param[in] size the size of the subshell
/// @param[in,out] ne the number of electrons, on return contains the number of
/// "remaining" electrons
template <typename Real>
void subshell_occvec(Real*& occvec, size_t size, size_t& ne) {
const auto ne_alloc = (ne > 2 * size) ? 2 * size : ne;
ne -= ne_alloc;
// # of electrons / orbital compute as precisely as possible
const double ne_per_orb = (ne_alloc % size == 0)
? static_cast<Real>(ne_alloc / size)
: (static_cast<Real>(ne_alloc)) / size;
for (size_t f = 0; f != size; ++f) occvec[f] = ne_per_orb;
occvec += size;
}
} // namespace detail
/// @param[in] Z the atomic number of the element
/// @throw if Z > 53
/// @return the number of STO-3G AOs for the element with atomic number \c Z
inline size_t sto3g_num_ao(size_t Z) {
size_t nao;
if (Z == 1 || Z == 2) // H, He
nao = 1;
else if (Z <= 10) // Li - Ne
nao = 5; // 2p is included even for Li and Be
else if (Z <= 18) // Na - Ar
nao = 9; // 3p is included even for Na and Mg
else if (Z <= 20) // K, Ca
nao = 13; // 4p is included
else if (Z <= 36) // Sc - Kr
nao = 18;
else if (Z <= 38) // Rb, Sr
nao = 22; // 5p is included
else if (Z <= 53) // Y - I
nao = 27;
else
throw "STO-3G basis is not defined for elements with Z > 53";
return nao;
}
/// @brief computes average orbital occupancies in the ground state of a neutral
/// atoms
/// @throw if Z > 53
/// @return occupation vector corresponding to the ground state electronic
/// configuration of a neutral atom with atomic number \c Z
/// corresponding to the orbital ordering in STO-3G basis
template <typename Real = double>
const std::vector<Real>& sto3g_ao_occupation_vector(size_t Z) {
static std::vector<Real> occvec(27, 0.0);
using detail::subshell_occvec;
occvec.resize(sto3g_num_ao(Z));
auto* occs_ptr = &occvec[0];
auto& occs = occs_ptr;
size_t num_of_electrons = Z; // # of electrons to allocate
// neutral atom electronic configurations from NIST:
// http://www.nist.gov/pml/data/images/illo_for_2014_PT_1.PNG
subshell_occvec(occs, 1, num_of_electrons); // 1s
if (Z > 2) { // Li+
subshell_occvec(occs, 1, num_of_electrons); // 2s
subshell_occvec(occs, 3, num_of_electrons); // 2p
}
if (Z > 10) { // Na+
subshell_occvec(occs, 1, num_of_electrons); // 3s
subshell_occvec(occs, 3, num_of_electrons); // 3p
}
if (18 < Z && Z <= 36) { // K .. Kr
// NB 4s is singly occupied in K, Cr, and Cu
size_t num_of_4s_electrons = (Z == 19 || Z == 24 || Z == 29) ? 1 : 2;
num_of_electrons -= num_of_4s_electrons;
subshell_occvec(occs, 1, num_of_4s_electrons); // 4s
size_t num_of_4p_electrons =
std::min(static_cast<decltype(Z)>(6), (Z > 30) ? Z - 30 : 0);
num_of_electrons -= num_of_4p_electrons;
subshell_occvec(occs, 3, num_of_4p_electrons); // 4p
subshell_occvec(occs, 5, num_of_electrons); // 3d
}
if (36 < Z && Z <= 53) { // Rb .. I
// 3d4s4p are fully occupied ...
subshell_occvec(occs, 1, num_of_electrons); // 4s
subshell_occvec(occs, 3, num_of_electrons); // 4p
// NB 5s is singly occupied in Rb, Nb, Mo, Ru, Rh, and Ag
size_t num_of_5s_electrons =
(Z == 37 || Z == 41 || Z == 42 || Z == 44 || Z == 45 || Z == 47) ? 1
: 2;
num_of_electrons -= num_of_5s_electrons;
subshell_occvec(occs, 1, num_of_5s_electrons); // 5s
size_t num_of_5p_electrons =
std::min(static_cast<decltype(Z)>(6), (Z > 48) ? Z - 48 : 0);
num_of_electrons -= num_of_5p_electrons;
subshell_occvec(occs, 3, num_of_5p_electrons); // 5p
subshell_occvec(occs, 5, num_of_electrons); // 3d
subshell_occvec(occs, 5, num_of_electrons); // 4d
}
return occvec;
}
} // namespace libint2
#endif // INCLUDE_LIBINT2_CHEMISTRY_STO3GATOMICDENSITY_H_
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