A5041750270- Diamond and Carbon-based Materials Research
- High-pressure geophysics and materials
- Graphene research and applications
- Particle Accelerators and Free-Electron Lasers
- Carbon Nanotubes in Composites
- Particle accelerators and beam dynamics
- Semiconductor materials and devices
- Ion-surface interactions and analysis
- Superconducting Materials and Applications
- Nuclear materials and radiation effects
- Advanced Chemical Physics Studies
- Quantum and electron transport phenomena
- Metal and Thin Film Mechanics
- Nuclear Materials and Properties
- Surface and Thin Film Phenomena
- Boron and Carbon Nanomaterials Research
- Molecular Junctions and Nanostructures
- X-ray Diffraction in Crystallography
- Semiconductor materials and interfaces
- Radioactive element chemistry and processing
- Force Microscopy Techniques and Applications
- Advanced Condensed Matter Physics
- Graphite, nuclear technology, radiation studies
- Electronic and Structural Properties of Oxides
- Fiber-reinforced polymer composites
Curtin University
2014-2024
The University of Sydney
2002-2020
Australian National University
2020
RMIT University
2020
Centre for Quantum Computation and Communication Technology
2005-2016
Daresbury Laboratory
1991-2014
Sci-Tech Daresbury
2014
Science and Technology Facilities Council
2012
Cockcroft Institute
2011-2012
University of Liverpool
2012
A transferable empirical potential for carbon is developed by extending the environment-dependent interaction proposed silicon. Generalized coordination functions, parametrized using ab initio data, describe dihedral rotation, nonbonded $\ensuremath{\pi}$-repulsion and fractional coordination. Elastic constants agree well with experiment, simulations of liquid compare very favorably Car-Parrinello calculations. Amorphous networks generated quench have properties superior to those Tersoff,...
The thermally induced transformation of kaolinite to metakaolin is simulated using molecular dynamics through a step-wise dehydroxylation approach. simulation shows that the removal structural water produces distortion or buckling effect in 1 : Al–Si layers, which due migration aluminium into vacant sites provided by inter-layer spacing. change characterized loss crystallinity and concomitant coordination from octahedral tetrahedral, with this study confirming presence 5-fold within...
The wastewater release from the Fukushima Daiichi nuclear plant is expected to have negligible effects on people and ocean
We develop a picture of graphenic crystallites within disordered carbons that goes beyond the traditional model graphitic platelets at random orientations. Using large atomistic structures containing one million atoms, we redefine meaning quantity La extracted from X-ray diffraction (XRD) patterns. Two complimentary approaches are used to measure size crystallites, which defined as regions regularly arranged hexagons. Firstly, calculate pattern directly coordinates and analyse them following...
Simulations are reported of a highly tetrahedral amorphous carbon network at density 3 g/cc using Car-Parrinello first principles molecular dynamics. The simulated structure consists 65% fourfold and 35% threefold coordinated sites, in good agreement with experiment. is also recent neutron diffraction data. An unexpected observation was the presence small rings containing as few three atoms. These triangles quadrilaterals, which resemble organic compounds cyclopropane cyclobutane, give...
The molecular-dynamics technique involving the rapid cooling of a liquid to simulate an amorphous solid has been used for several years. Despite success technique, method lacked physical justification, and rates have assumed be too fast. In this paper analysis thermal spike times in tetrahedral carbon shows that is reasonable are appropriate. Using three independent methods it found cools less than picosecond, considerably faster previously recognized. An algorithm suitable estimating...
Amorphous carbon networks are used to test various levels of theoretical approaches molecular dynamics simulations. The density-functional theory as implemented in the Car-Parrinello method, nonorthogonal tight-binding environment-dependent interaction potential (EDIP), and Brenner compared directly liquid quench simulations containing 125 atoms at four densities. We find that low densities predictions agreement with those from theory, while structures produced by method compare well all...
Simulations are reported of a highly tetrahedral amorphous carbon network at density 2.9 g/${\mathrm{cm}}^{3}$ using Car-Parrinello first principles molecular dynamics. The was generated by cooling liquid sample 64 atoms to form an structure. simulated structure is in good agreement with recent neutron diffraction data and contains 65% fourfold- 35% threefold-coordinated sites. Three- four-membered rings present the give unusual topology. Evidence from organic chemistry shown support...
An improved method for the modelling of carbon structures based on a hybrid reverse Monte Carlo (HRMC) is presented. This algorithm incorporates an accurate environment dependent interaction potential (EDIP) in conjunction with commonly used constraints derived from experimental data. In this work, we compare new other results small system 2.9 g/cc amorphous carbon. We find that approach greatly improves structural description, alleviating common problem standard (RMC) generating high...
Pure carbon phases such as fullerenes, nanotubes, and graphite are archetypal examples of the self-organizing capability $s{p}^{2}$-bonded carbon. Naturally occurring phenomena a wide variety experimental apparatus known to produce highly ordered carbons if temperature or energy process is sufficiently high. Here we present molecular-dynamics simulations $s{p}^{2}$ ordering using disordered amorphous precursors. Using environment-dependent interaction potential describe interatomic forces,...
The breakdown of the diamond lattice is explored by ion implantation and molecular dynamics simulations. We show that strain-driven, rather than damage-driven, persists until 16% atoms have been removed from their sites. figure shows transition between amorphous carbon diamond, with interfaces highlighted dashed lines. Detailed facts importance to specialist readers are published as ”Supporting Information”. Such documents peer-reviewed, but not copy-edited or typeset. They made available...
The environment-dependent interaction potential is a transferable empirical for carbon which well suited studying disordered systems. Ab initio data are used to motivate and parametrize the functional form, includes environment-dependence in pair triple terms, generalized aspherical coordination describing dihedral rotation non-bonded π-repulsion. Simulations of liquid compare very favourably with Car-Parrinello calculations, while amorphous networks generated by quench have properties...
We demonstrate that when, and only the biaxial stress is increased above a critical value of $6\ifmmode\pm\else\textpm\fi{}1\text{ }\text{ }\mathrm{GPa}$ during growth carbon film at room temperature, tetrahedral amorphous formed. This confirms present formation an determines its $s{p}^{3}$ bonding fraction. In vicinity stress, highly oriented graphitelike material formed which exhibits low electrical resistance provides Ohmic contacts to silicon. Atomistic simulations reveal structural...
Molecular dynamics simulation is used to study radiation damage cascades in graphite. High statistical precision obtained by sampling a wide energy range (100–2500 eV) and large number of initial directions the primary knock-on atom. Chemical bonding described using Environment Dependent Interaction Potential for carbon. Graphite found exhibit response distinct from metals oxides primarily due absence thermal spike which results point defects disconnected regions damage. Other unique...
Glassy carbon is a technologically important material with isotropic properties that nongraphitizing up to ∼3000 °C and displays complete or "superelastic" recovery from large compression. The pressure limit of these not yet known. Here we use experiments modeling show permanent densification, preferred orientation occurs in glassy loaded 45 GPa above, where represents the superelastic material. changes are explained by transformation its sp^{2} rich starting structure sp^{3} phase reverts...
Abstract Lateral slicing of micron length carbon nanotubes (CNTs) is effective on laser irradiation the materials suspended within dynamic liquid thin films in a microfluidic vortex fluidic device (VFD). The method produces sliced CNTs with minimal defects absence any chemical stabilizers, having broad distributions centred at ca 190, 160 nm and 171 for single, double multi walled respectively, as established using atomic force microscopy supported by small angle neutron scattering solution...
Disordered carbons comprise graphene fragments assembled into three-dimensional networks. It has long been debated whether these networks contain positive curvature, as seen in fullerenes, negative proposed for the schwarzite structures, or zero ribbons. We present a mesh-based approach to analyze topology of set nanoporous and glassy carbon models that accurately reproduce experimental properties. Although all three topological elements are present, negatively curved structures dominate. At...
Using density functional theory and guided by extensive scanning tunneling microscopy (STM) image data, we formulate a detailed mechanism for the dissociation of phosphine (PH3) molecules on Si(001) surface at room temperature. We distinguish between main sequence that involves PH2+H, PH+2H, P+3H as observable intermediates, secondary gives rise to PH+H, P+2H, isolated phosphorus adatoms. The latter arises because PH2 fragments are surprisingly mobile can diffuse away from third hydrogen...