First zigzagging problem

For a calculation of the IRC, we have to start at the saddle point Xo=x(0), but the first step has to be forced in direction of the negative main curvature of the PES, because it is g(xo)=0 at the saddle point, and eq.(4) would not start to work. After starting algorithm (4), it is sure to reach a minimizer of the PES. Sometimes numerical problems emerge through the zigzagging of the numerical SDP near the PES minimum, or in a fiat part of the valley of the PES [12,14]. 

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