Thanks for all the ideas. In the end I found the best way is to use ^:{} as options, and then use regular subscripts. For chemical formulas works fine. So that is ABO_{3} and ABO_{3-\delta}.
John
----------------------------------- John Kitchin Associate Professor Doherty Hall A207F Department of Chemical Engineering Carnegie Mellon University
Pittsburgh, PA 15213 412-268-7803 http://kitchingroup.cheme.cmu.edu