1. Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Minami-ohsawa 1-1, Hachioji, Tokyo 192-0397, Japan, “Structural Ordering and Physical Properties,” PRESTO, Japan Science and Technology Corporation, Japan, X-ray Research Laboratory, Rigaku Co., Ltd., 3-9-12 Matsubara-cho, Akishima, Tokyo 196-8666, Japan, and Centre de Recherche Paul Pascal, CNRS UPR 8641, 115 Avenue du Dr. A. Schweitzer, 33600 Pessac, France