add exchange gradients and density broyden

src/tblite/exchange.f90

@@ -0,0 +1,33 @@
+module tblite_exchange
+   use mctc_env, only : wp
+   use tblite_mulliken_kfock, only : mulliken_kfock_type, new_mulliken_exchange
+   use mctc_io, only : structure_type
+   use tblite_param_exchange, only : exchange_record
+   use tblite_exchange_type, only : exchange_type
+   use tblite_basis_type, only : basis_type
+   implicit none
+   private
+   public :: new_exchange
+
+contains
+subroutine new_exchange(self, mol, hardness, par, bas)
+   !> Instance of the multipole container
+   class(exchange_type), allocatable ,intent(inout) :: self
+   !> Molecular structure data
+   type(structure_type), intent(in) :: mol
+   real(wp), intent(in) :: hardness(:)
+   type(exchange_record) :: par
+   type(basis_type) :: bas
+
+   if (par%mulliken) then
+      block
+         type(mulliken_kfock_type), allocatable :: tmp
+         allocate(tmp)
+         call new_mulliken_exchange(tmp, mol, hardness, .false., .false., par%frscale, &
+            & par%omega, par%lrscale, par%average, par%expsmooth, bas)
+         call move_alloc(tmp, self)
+      end block
+   end if
+end subroutine
+
+end module tblite_exchange

src/tblite/exchange/cache.f90

@@ -0,0 +1,34 @@
+module tblite_exchange_cache
+   use mctc_env, only : wp, dp
+   use mctc_io, only : structure_type
+   use tblite_coulomb_ewald, only : get_alpha
+   use tblite_wignerseitz, only : wignerseitz_cell, new_wignerseitz_cell
+   implicit none
+   private
+
+   public :: exchange_cache
+
+
+   type :: exchange_cache
+      real(dp), allocatable :: curr_D(:, :)
+      real(dp), allocatable :: ref_D(:, :)
+      real(dp), allocatable :: prev_F(:, :)
+      real(dp), allocatable :: gamma_(:,:)
+   contains
+      procedure :: update
+   end type exchange_cache
+
+
+contains
+
+
+subroutine update(self, mol)
+   !> Instance of the electrostatic container
+   class(exchange_cache), intent(inout) :: self
+   !> Molecular structure data
+   type(structure_type), intent(in) :: mol
+
+
+end subroutine update
+
+end module tblite_exchange_cache

src/tblite/exchange/meson.build

@@ -0,0 +1,21 @@
+# This file is part of tblite.
+# SPDX-Identifier: LGPL-3.0-or-later
+#
+# tblite is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# tblite 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 Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with tblite.  If not, see <https://www.gnu.org/licenses/>.
+
+srcs += files(
+  'cache.f90',
+  'mulliken_kfock.f90',
+  'type.f90'
+)