1. Research Institute for Computational Sciences (RICS), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan, and Accelrys K.K., Nishishinbashi TS Building, 3-3-1 Nishishinbashi, Minato-ku, Tokyo 105-0003, Japan