QCaml/Basis/Overlap.ml

open Util
open Constants
open Lacaml.D

type t = Mat.t

module Am  = AngularMomentum
module Bs  = Basis
module Co  = Coordinate
module Cs  = ContractedShell
module Csp = ContractedShellPair
module Po  = Powers
module Psp = PrimitiveShellPair

let cutoff = integrals_cutoff

let to_powers x = 
  let open Zkey in
  match to_powers x with
  | Six x -> x
  | _ -> assert false

(** Computes all the overlap integrals of the contracted shell pair *)
let contracted_class shell_a shell_b : float Zmap.t = 

  match Csp.make shell_a shell_b with
  | Some shell_p -> 
    begin

  (* Pre-computation of integral class indices *)
  let class_indices = Csp.zkey_array shell_p in

  let contracted_class = 
    Array.make (Array.length class_indices) 0.
  in

  let a_minus_b = 
    Csp.a_minus_b shell_p
  in
  let norm_coef_scales =
    Csp.norm_scales shell_p
  in

  (* Compute all integrals in the shell for each pair of significant shell pairs *)

  let xyz_of_int k =
    match k with
    | 0 -> Co.X
    | 1 -> Co.Y
    | _ -> Co.Z
  in

  List.iter (fun (coef_prod, psp) ->
      (** Screening on thr product of coefficients *)
      if (abs_float coef_prod) > 1.e-3*.cutoff then
        begin
          let expo_inv = Psp.exponent_inv psp
          and center_pa = Psp.center_minus_a psp
          in

          Array.iteri (fun i key ->
              let (angMomA,angMomB) = to_powers key in
              let f k = 
                let xyz = xyz_of_int k in
                Overlap_primitives.hvrr (Po.get xyz angMomA, Po.get xyz angMomB)  
                  expo_inv
                  (Co.get xyz a_minus_b,
                  Co.get xyz center_pa) 
              in
              let norm =  norm_coef_scales.(i) in
              let integral = chop norm (fun () -> (f 0)*.(f 1)*.(f 2)) in 
              contracted_class.(i) <- contracted_class.(i) +. coef_prod *. integral
            ) class_indices
        end
    ) (Csp.coefs_and_shell_pairs shell_p);
  let result = 
    Zmap.create (Array.length contracted_class)
  in
  Array.iteri (fun i key -> Zmap.add result key contracted_class.(i)) class_indices;
  result
  end
  | None -> Zmap.create 0


(** Create overlap matrix *)
let of_basis basis =
  let to_powers x = 
    let open Zkey in
    match to_powers x with
    | Three x -> x
    | _ -> assert false
  in

  let n     = Bs.size basis
  and shell = Bs.contracted_shells basis
  in

  let result = Mat.create n n in
  for j=0 to (Array.length shell) - 1 do
    for i=0 to j do
      (* Compute all the integrals of the class *)
      let cls =
        contracted_class shell.(i) shell.(j) 
      in

      Array.iteri (fun j_c powers_j ->
          let j_c = Cs.index shell.(j) + j_c + 1 in
          let xj = to_powers powers_j in
          Array.iteri (fun i_c powers_i ->
              let i_c = Cs.index shell.(i) + i_c + 1 in
              let xi = to_powers powers_i in
              let key = 
                Zkey.of_powers_six xi xj
              in
              let value = 
                try Zmap.find cls key 
                with Not_found -> 0.
              in
              result.{i_c,j_c} <- value;
              result.{j_c,i_c} <- value;
            ) (Am.zkey_array (Singlet (Cs.ang_mom shell.(i))))
        ) (Am.zkey_array (Singlet (Cs.ang_mom shell.(j))))
    done;
  done;
  Mat.detri result;
  result



(** Write all overlap integrals to a file *)
let to_file ~filename overlap =

  let oc = open_out filename in
  let n =
    Mat.dim1 overlap 
  in

  for j=1 to n  do
    for i=1 to j do
      if (abs_float overlap.{i,j} > cutoff) then
        Printf.fprintf oc "%4d %4d %20.12e\n" i j overlap.{i,j}
    done;
  done;
  close_out oc