1. Contribution from the Angstrom Technology Partnership, Joint Research Center for Atom Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-0046, Japan, National Institute of Advanced Industrial Science and Technology, Joint Research Center for Atom Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562, Japan, and Research Institute for Computational Sciences, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan