Computer Physics Communications 141 (2001) 1–16 www.elsevier.com/locate/cpc MD simulation of cluster–surface impacts for metallic phases: soft landing, droplet spreading and implantation Kholmirzo Kholmurodov a,∗ , Igor Puzynin b , William Smith c , Kenji Yasuoka d , Toshikazu Ebisuzaki a a Computational Science Division, Advanced Computing Center, The Institute of Physical and Chemical Research (RIKEN), Hirosawa 2-1, Wako, Saitama 351-0198, Japan b Laboratory of Information Technologies, Joint Institute for Nuclear Research, Dubna, Moscow region, 141980, Russia c Daresbury Laboratory, Daresbury, Warrington, Cheshire, UK d Department of Mechanical Engineering, Keio University, Japan Received 18 December 2000; accepted 15 May 2001 Abstract An optimized version of the DL_POLY molecular dynamics simulation code [K. Kholmurodov, W. Smith, K. Yasuoka, T. Ebisuzaki, Comput. Phys. Commun. 125 (2000) 167–192] has been used to study the cluster–surface impact processes for metallic phases. The interaction of an energetic cluster of atoms with a solid surface has been investigated using the Finnis–Sinclair many-body potential. The characteristics of the cluster–surface collisions were studied in a wide range of the cluster impact energies (E inc = 0.035–3.5 eV/atom). Modification of the surface, exposed to the cluster-beams, was studied by monitoring the molecular dynamics configurations of the system in real time. The density and temperature distributions in the system under the energetic irradiations has been investigated in detail. The three major channels of the impact yield (viz., soft landing, droplet spreading and implantation) were distinguished and estimated. Based on the density and temperature distributions data the low energy cluster–surface impact has been analyzed and a novel interpretation of droplet spreading process is given.  2001 Elsevier Science B.V. All rights reserved. Keywords: Molecular dynamics simulation; DL_POLY code; Clusters; Solid surface; Large system; Impact processes 1. Introduction As is known [1–3], one of the effective methods of materials synthesis for modern technologies is elec- tron and ion surface treatment in a pulse explosion regime. Energy deposition in a thin surface layer by high-power electron and ion beams may lead to a completely new structure on the surface, which may * Corresponding author. E-mail address: mirzo@atlas.riken.go.jp (K. Kholmurodov). possess practically interesting physical and chemical properties [2,4,5]. Over about three decades ion beams have been used to modify materials in the manufacture of integrated circuits [6–8]. One of the aspects of elec- tron and ion irradiation of materials is the transforma- tion of such material parameters, which is of great in- terest in metallurgy. For example, ion and electron ir- radiation of metals may change the metal hardness, fa- tigue and corrosion resistance and essentially increase their strength [2,9,10]. We note also the use of beam modifications for hardening and improving the tribo- 0010-4655/01/$ – see front matter  2001 Elsevier Science B.V. All rights reserved. PII:S0010-4655(01)00292-2