ИСТИНА

The mathematical problem of calculating molecular force fields within the general approximation of small vibrations (harmonic model) is an ill-posed problem and it does not satisfy any of the three well-posedness conditions (existence of solution, its uniqueness and stability to perturbations in input data). In most cases, the main difficulty is non-uniqueness of solution. Different algorithms based on the theory of regularization of nonlinear ill-posed problems have been proposed for solviing this problem and finfing the sets of force constants. In our strategy the stabilizing matrix F0 is chosen as a result of quantum mechanical calculations, and thus we search for matrix F which is the nearest by the chosen Euclidean norm to the given ab initio F0. The optimized solution is referred to as Regularized Quantum Mechanical Force Field (RQMFF).