1. Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan
2. The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
3. Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan
4. NanoMaterials Research Institute, Kanazawa University, Kanazawa 920-1192, Japan