mqc_method_hf.f90 Source File

!! Hartree-Fock method implementation for metalquicha
module mqc_method_hf
   !! Implements the Hartree-Fock quantum chemistry method
   !! Provides energy and gradient calculations using a basic SCF procedure.
   use pic_types, only: dp
   use mqc_method_base, only: qc_method_t
   use mqc_result_types, only: calculation_result_t
   use mqc_physical_fragment, only: physical_fragment_t
   implicit none
   private

   public :: hf_method_t, hf_options_t

   type :: hf_options_t
      !! Hartree-Fock calculation options
      character(len=32) :: basis_set = 'sto-3g'
         !! Basis set name
      logical :: spherical = .true.
         !! Use spherical (true) or Cartesian (false) basis
      logical :: verbose = .false.
         !! Print SCF iterations

      ! SCF settings (from shared scf_config_t)
      integer :: max_iter = 100
         !! Maximum SCF iterations
      real(dp) :: conv_tol = 1.0e-8_dp
         !! Energy convergence threshold
      real(dp) :: density_tol = 1.0e-6_dp
         !! Density matrix convergence threshold
      logical :: use_diis = .true.
         !! Use DIIS acceleration
      integer :: diis_size = 8
         !! Number of Fock matrices for DIIS
   end type hf_options_t

   type, extends(qc_method_t) :: hf_method_t
      !! Hartree-Fock method implementation
      type(hf_options_t) :: options
   contains
      procedure :: calc_energy => hf_calc_energy
      procedure :: calc_gradient => hf_calc_gradient
      procedure :: calc_hessian => null_hessian  !! Placeholder for Hessian calculation
   end type hf_method_t

contains

   subroutine hf_calc_energy(this, fragment, result)
      !! Calculate electronic energy using Hartree-Fock method
      class(hf_method_t), intent(in) :: this
      type(physical_fragment_t), intent(in) :: fragment
      type(calculation_result_t), intent(out) :: result

      ! DUMMY IMPLEMENTATION
      ! TODO: Implement actual HF calculation
      ! 1. Convert fragment%basis to libcint format
      ! 2. Build one-electron integrals (S, T, V)
      ! 3. Run SCF iterations
      ! 4. Calculate final energy

      print *, "HF: Calculating energy for fragment with", fragment%n_atoms, "atoms"
      print *, "HF: nelec =", fragment%nelec
      print *, "HF: charge =", fragment%charge
      print *, "HF: multiplicity =", fragment%multiplicity

      ! Dummy result
      result%energy%scf = -1.0_dp  ! Placeholder
      result%has_energy = .true.

      print *, "HF: Dummy energy =", result%energy%total()

   end subroutine hf_calc_energy

   subroutine hf_calc_gradient(this, fragment, result)
      !! Calculate energy gradient using Hartree-Fock method
      class(hf_method_t), intent(in) :: this
      type(physical_fragment_t), intent(in) :: fragment
      type(calculation_result_t), intent(out) :: result

      ! DUMMY IMPLEMENTATION
      ! TODO: Implement gradient calculation
      ! 1. Calculate energy (call calc_energy)
      ! 2. Calculate gradient using integral derivatives

      print *, "HF: Calculating gradient for fragment with", fragment%n_atoms, "atoms"

      ! First get energy
      call this%calc_energy(fragment, result)

      ! Allocate and fill dummy gradient
      allocate (result%gradient(3, fragment%n_atoms))
      result%gradient = 0.0_dp  ! Placeholder
      result%has_gradient = .true.

      print *, "HF: Dummy gradient allocated"

   end subroutine hf_calc_gradient

   subroutine null_hessian(this, fragment, result)
      !! Placeholder for Hessian calculation
      class(hf_method_t), intent(in) :: this
      type(physical_fragment_t), intent(in) :: fragment
      type(calculation_result_t), intent(out) :: result

      print *, "HF: Hessian calculation not implemented yet."
      result%has_hessian = .false.

   end subroutine null_hessian

end module mqc_method_hf