1. Institute for Theoretical and Experimental Physics, ITEP, Moscow 117259, Russia
2. Research Development Institute of Power Energy RDIPE, P.O.B. 788, Moscow 101000, Russia
3. Institute for Neorganic Materials, VNIINM, Moscow 123060, Russia
4. Los Alamos National Laboratory T-2, MS B242, Los Alamos, New Mexico 87545
5. Bogoliubov Laboratory of Theoretical Physics JINR, Dubna 141980, Russia
6. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831