ABSTRACT
The frequency determination in an exponential fitting multi-step method is a question without a definite answer. In most of the cases, the estimation of the frequency arises from the nature of the problem, as in the Schrödinger equation. Another approach is to select a frequency which increases the order of the method by zeroing the first non vanishing term of the linear truncation error. In this work, two general methods are exploited: the first is applicable to equations of the form y"(x) = f(x,y) and relates the frequency with the coefficient of y in f(x, y) while the other connects the frequency with the curvature of the solution.
