diff --git a/qcaml/lib/dune b/qcaml/lib/dune
new file mode 100644
index 0000000..6f107cf
--- /dev/null
+++ b/qcaml/lib/dune
@@ -0,0 +1,14 @@
+; name = name of the supermodule that will wrap all source files as submodules
+; public_name = name of the library for ocamlfind and opam
+(library
+ (name qcaml)
+ (public_name qcaml)
+ (libraries
+        qcaml.common
+        qcaml.particles
+        qcaml.gaussian_basis
+        qcaml.gaussian_integrals
+	qcaml.operators
+	qcaml.ao
+ )
+ (synopsis "Main QCaml entry point"))
diff --git a/qcaml/lib/simulation.ml b/qcaml/lib/simulation.ml
new file mode 100644
index 0000000..dc8e314
--- /dev/null
+++ b/qcaml/lib/simulation.ml
@@ -0,0 +1,45 @@
+open Common
+open Particles
+open Operators
+    
+type t = {
+  charge            : Charge.t;
+  electrons         : Electrons.t;
+  nuclei            : Nuclei.t;
+  ao_basis          : Ao.Basis.t;
+  operators         : Operator.t list;
+}
+
+let nuclei            t = t.nuclei
+let charge            t = t.charge
+let electrons         t = t.electrons
+let ao_basis          t = t.ao_basis
+let nuclear_repulsion t = Nuclei.repulsion @@ nuclei t
+let operators         t = t.operators
+
+let make ?(multiplicity=1)
+      ?(charge=0)
+      ?(operators=[])
+      ~nuclei
+      ao_basis
+  =
+
+  (* Tune Garbage Collector *)
+  let gc = Gc.get () in
+  Gc.set { gc with space_overhead = 1000  };
+
+  let electrons =
+    Electrons.of_atoms ~multiplicity ~charge nuclei
+  in
+
+  let charge = 
+    Charge.(Nuclei.charge nuclei + Electrons.charge electrons)
+  in
+
+  {
+    charge ; nuclei ; electrons ; ao_basis ; 
+    operators
+  }
+
+
+
diff --git a/qcaml/lib/simulation.mli b/qcaml/lib/simulation.mli
new file mode 100644
index 0000000..285489e
--- /dev/null
+++ b/qcaml/lib/simulation.mli
@@ -0,0 +1,32 @@
+(* Contains the state of a simulation *)
+
+open Common
+open Particles
+open Operators
+    
+type t
+
+val nuclei : t -> Nuclei.t
+(** Nuclear coordinates used in the smiulation *)
+
+val charge : t -> Charge.t
+(** Total charge (electrons + nuclei) *)
+
+val electrons : t -> Electrons.t
+(** Electrons used in the simulation *)
+
+val ao_basis : t -> Ao.Basis.t
+(** Atomic basis set *)
+
+val nuclear_repulsion : t -> float
+(** Nuclear repulsion energy *)
+
+val operators : t -> Operator.t list
+(** List of extra operators (range-separation, f12, etc) *)
+
+(** {1 Creation} *)
+
+val make : ?multiplicity:int -> ?charge:int -> 
+  ?operators:Operator.t list-> nuclei:Nuclei.t ->
+  Ao.Basis.t -> t
+