1. Institute of Scientific and Industrial ResearchOsaka University Suita Osaka, 567‐0047 Japan
2. Riken Center for Computational Science Kobe Hyogo 650‐0047 Japan
3. Department of Chemistry, Graduate School of ScienceOsaka University Suita Osaka 560‐0043 Japan
4. Research Institute for Interdisciplinary ScienceOkayama University Okayama Okayama 700‐8530 Japan
5. Center of Computational SciencesTsukuba University Tsukuba Ibaraki 305‐8577 Japan