Eur. Phys. J. D (2015) 69: 35
https://doi.org/10.1140/epjd/e2014-50785-x

Regular Article

Ultrafast laser irradiation of spherical nanoparticles: molecular-dynamics results on fragmentation and small-angle scattering

¹ Physics Department and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schrödinger-Straße, 67663 Kaiserslautern, Germany
² Department of Physics, State University of Jakarta, Jl. Pemuda 10, 13220 Jakarta Timur, Indonesia

^a e-mail: urbassek@rhrk.uni-kl.de

Received: 4 November 2014
Received in final form: 26 November 2014
Published online: 3 February 2015

Abstract

Using molecular dynamics simulation we study the response of a spherical nanoparticle to a sudden homogeneous energization, such as effected by ultrashort pulse laser irradiation. We consider a Lennard-Jones model system and two different values of the energization. For the smaller one, the sphere expands while a multitude of voids are created inside; the sphere develops finally into an external shell filled with gas and small clusters. For the higher energization, the sphere expands uniformly and no shell structure is formed. An analysis of the pressure generated confirms that in the latter case the pressure is compressive throughout the sphere expansion, while it is temporarily tensile for the lower energization leading to void formation. The final state of both systems shows the fragmentation of the sphere into a multitude of clusters. With increasing fragmentation the cluster distribution becomes shifted to smaller sizes. Simulated small-angle scattering functions of the exploding NP are presented. The distribution of minima allows for an easy determination of the particle size during expansion.