Molecular dynamics investigations of modulated phases in organic materials

Abstract

In order to apply the molecular dynamics (MD) method to simulate modulated phases in organic materials, a compensating external pressure tensor is proposed to compensate for the de®ciencies of the force ®eld applied in the simulation. MD can well reproduce modulated phases that have been measured by diffraction. Mechanisms of incommensurate modulation are revealed from the simulations. Details of the structures relating to the origins and mechanisms giving rise to the formation of modulated phases are presented.

Teaching general chemistry, solid-state chemistry and crystallography in one comprehensive undergraduate course: can the effect be synergistic?

“…We not only explain the basics of describing such structures but focus on the possible reasons why a structure can become modulated (in terms of the 'conflict' between the requirements imposed by the interactions between the closest and more distant neighbours in the structure, or as an 'intermediate state' between 'ordinary' periodic structures). In this respect, we discuss the studies of incommensurate structures as a probe to reveal atomic interactions in crystals (Arakcheeva et al, 2005;Chapuis & Arakcheeva, 2004;Pan & Chapuis, 2005). We consider modulations resulting from displacements, rotations, changes in the magnetic momentum and partial occupancy of positions.…”