Generation of Intrinsic Vibrational Gap Modes in Three-Dimensional Ionic Crystals

TL;DR

This paper demonstrates the existence of intrinsic localized vibrational gap modes in perfect 3D ionic crystals using molecular dynamics simulations, revealing stable anharmonic localized vibrations in NaI structures.

Contribution

It introduces the first molecular dynamics evidence of intrinsic localized gap modes in perfect 3D ionic crystals, highlighting their stability and structural features.

Findings

Localized gap modes exist in NaI crystals.

Modes are stable for at least 200 cycles.

Zinc blende structure favors easier formation.

Abstract

The existence of anharmonic localization of lattice vibrations in a perfect 3-D diatomic ionic crystal is established for the rigid-ion model by molecular dynamics simulations. For a realistic set of NaI potential parameters, an intrinsic localized gap mode vibrating in the [111] direction is observed for fcc and zinc blende lattices. An axial elastic distortion is an integral feature of this mode which forms more readily for the zinc blende than for the fcc structure. Molecular dynamics simulations verify that in each structure this localized mode may be stable for at least 200 cycles.