A REDUCED-RESTRICTED-QUASI-NEWTON-RAPHSON-METHOD FOR LOCATING AND OPTIMIZING ENERGY CROSSING POINTS BETWEEN 2 POTENTIAL-ENERGY SURFACES

We present a method for the location and optimization of an intersecti on energy point between two potential energy surfaces. The procedure d irectly optimizes the excited state energy using a quasi-Newton-Raphso n method coupled with a restricted step algorithm. A linear transforma tion is also used for the solution of the quasi-Newton-Raphson equatio ns. The efficiency of the algorithm is analyzed and demonstrated in so me examples. (C) 1997 by John Wiley & Sons, Inc.