T. Mattila

Simulation of radiation induced structural transformation in glassy metals

Abstract Radiation induced structural damage in metallic glasses has been investigated using Molecular Dynamics simulation. Three different models were explored, possessing pronounced icosahedral local order, which represented both monatomic glass and the amorphous Ni-P alloy. The paper presents detailed analysis of the structural disorder induced by the collision cascade imitating the radiation effect, as well as its evolution in time.

Hillock formation on ion-irradiated graphite surfaces

Abstract Scanning probe microscopy experiments show that ion irradiation of (0001) graphite results in the formation of isolated defects comprising of a few tens of atoms. We use molecular dynamics simulations and density-functional theory calculations to study the formation probabilities of these defects. We identify different defect structures which correspond to experimentally observed hillocks on graphite surfaces. We find that the predominant source of defects are vacancies and interlayer interstitials, and identify a three-atom carbon ring defect on the graphite surface.

Computational modelling of atomic-scale defect phenomena in compound semiconductors

This article summarizes recent work of first-principles simulation of atomic-scale defects in compound semiconductors. The calculations are based on the pseudopotential-plane wave techniques for density-functional theory. We discuss the structural and electronic properties of various point defects and their complexes. In particular, we focus on defect-induced metastabilities and compensation mechanisms due to defect-dopant pairing. The materials discussed in detail are GaAs, GaN, A1N and ZnSe.