Soliton dynamics in a formamide stack using a Taylor-series expansion for the potential surface: The Hartree-Fock potential

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Abstract
The Hartree-Fock potential surface of a stacked formamide dimer is fitted with a Taylor series of sixth order in three geometrical degrees of freedom. Using this potential, molecular dynamics in formamide stacks are studied. The existence of solitary waves is numerically shown. Furthermore, it is shown that the phenomenon is due to the nonlinear part of the forces. These waves are produced by distortions of the geometry at the chain ends as well as in the middle of the chain. In the latter case two waves traveling in opposite directions are formed. Two solitary waves survive collisions without considerable perturbations. The velocities of the different kinds of waves are intrinsic properties of the system, being independent of the kinetic energy transported. The kinetic mass of the waves is rather high (up to 900 electron masses) depending on the energy carried by the waves. A lower limit of the excitation energy for creating a solitary wave could not be found.