Determination of precise harmonic force constants for alanine polypeptides

We have developed a precise harmonic force field for alanine polypeptides extracted directly from the Hessian tensor of density functional theory calculations. The results yield force constants with very small deviations among the bonds and angles of different size of polypeptides providing a force field that reproduces the vibrational spectrum needed to perform molecular dynamics simulations focusing in the use of the vibrational spectrum to transfer information. In this first principles method, no fitting procedures are used in the formalism for the generation of force field constants.