(**  Data structure containing the number of alpha and beta electrons.
  *)

type t

open Common

(** Creation *)

val make : int -> int -> t
(* make n_alfa n_beta *)

val of_atoms : ?multiplicity:int -> ?charge:int -> Nuclei.t -> t
(** Creates the data relative to electrons for a molecular system described by
    Nuclei.t for a given total charge and spin multiplicity. 

   @param multiplicity default is 1
   @param charge       default is 0
   @raise Invalid_argument if the spin multiplicity is not compatible with
    the molecule and the total charge.
*)

(** Access *)

val charge       : t -> Charge.t
(**  Sum of the charges of the electrons *)

val n_elec       : t -> int
(* Number of electrons *)

val n_alfa       : t -> int
(* Number of alpha electrons *)

val n_beta       : t -> int
(* Number of beta  electrons *)

val multiplicity : t -> int
(* Spin multiplicity: 2S+1 *)


(** Printers *)

val pp : Format.formatter -> t -> unit