def _create_occupation_file(self, run_type="rks"):
        self.cd_work_dir("create occ")

        self._setup_pdf()

        occ_level = -1
        electrons_per_orb = 0.0
        run_type = run_type.upper()
        if run_type == "RKS":
            occ_level = int((self.pdfparam.num_of_electrons / 2.0))
            electrons_per_orb = 2.0
        else:
            logger.critical(
                "{header} NOT supported. run_type={run_type}".format(
                    header=self.header, run_type=run_type
                )
            )

        # num_of_MOs = self.pdfparam.num_of_MOs
        # occ_vtr = pdf.Vector(num_of_MOs)
        occ_vtr = pdf.Vector(occ_level)
        for i in range(occ_level):
            occ_vtr.set(i, electrons_per_orb)

        occ_vtr_path = "guess.occ.{}.vtr".format(run_type.lower())
        occ_vtr.save(occ_vtr_path)
        self._check_path(occ_vtr_path)

        self.save()
        self.restore_cwd()