Extended multistate CASPT2 (XMS-CASPT2) [see T. Shiozaki, W. Gyorffy, P. Celani, and H.-J. Werner,
Communication: The extended multi-state CASPT2 method: Energy and nuclear gradients,
J. Chem. Phys. 135, 081106 (2011)] provides a better description of near degenerate
situations and avoided crossings. Currently this option is available only with the RS2
code, not for RS2C.