Vibron-vibron coupling from ab initio molecular dynamics simulations of a silicon cluster

Abstract

We study the temperature dependent dynamical processes of a Si10H16 cluster and obtain a blue shift of the Si-Si vibrational modes with transverse acoustic character and a red shift of the other vibrational modes with increasing temperature. We link this behavior to the bond length expansion and the varying sign of the Grueneisen parameter. We further present a computational approach able to extract the vibron-vibron coupling strength in clusters or molecules. Our approach is based on ab initio Born-Oppenheimer molecular dynamics and a projection formalism able to deliver the individual vibron occupation numbers. From the Fourier transform of the vibron energy autocorrelation function we obtain the coupling strength of each vibron to the most strongly coupled vibronic states. We find vibron-vibron coupling strength up to 2.5 THz with a moderate increase of about 5 % when increasing the temperature from 50 to 150 K.

14 pages, 8 figures

References in corpus (8)

• Molecular Transport Junctions: Vibrational Effects
• Heavily Doped Semiconductor Nanocrystal Quantum Dots
• Phonon anharmonicities in graphite and graphene
• Device-scale perpendicular alignment of colloidal nanorods
• Polaron relaxation in self-assembled quantum dots: Breakdown of the semi-classical model
• Confinement effects on the vibrational properties of III-V and II-VI nanoclusters
• Phonon-phonon interactions and phonon damping in carbon nanotubes
• Ab-initio calculation of the vibrational modes of SiH4, H2SiO, Si10H16, and Si10H14O