11 December 2009
Atomistic computer simulation models are constructed to study a range of materials in which the atoms appear in novel environments. Two key research areas are considered: • The Growth and Structure Inorganic Nanotubes. A range of materials have been observed to form nanotubular structures (inorganic nanotubes - INTs) analogous to those well known for carbon. These INTs, which may have unique low-dimensional morphologies not simply related to known bulk polymorphs, potentially offer unique mechanical and electronic properties. A useful synthetic pathway is to use carbon nanotubes as templates using molten salts. Atomistic simulation models, in which the atom interactions are treated utilizing relatively simple potential energy functions, are developed and applied to understand the INT formation and stability. INT morphologies are classified by reference to folding two dimensional sheets. The respective roles of thermodynamics and kinetics in determining INT morphology are outlined and the atomistic results used to develop an analytic model to predict INT diameters. • Ordering on Multiple Length-Scales in Network-forming Liquids. Intermediate-range order (IRO), in which systems exhibit structural ordering on length-scales beyond the nearest-neighbour (short-range), has been identified in a wide range of materials and is characterised by the appearance of the so-called first sharp diffraction peak (FSDP) at low scattering angles. The precise structural origin of such ordering remains contentious and a full understanding of the factors underlying this order is vital if such materials (many of which are technologically significant) are to be produced in a controlled manner. Simulation models, in which the ion-ion interactions are represented by relatively simple potential functions which incorporate (many-body) polarisation and which are parameterised by reference to well-directed electronic structure calculations, have been shown to reproduce such IRO and allow the precise structural origin of the IRO to be identified. Furthermore, the use of relatively simple (and hence computationally tractable) models allows for the study of the relatively long length- and time-scales required. The underlying structures are analysed with reference to both recent (neutron scattering) experimental results and high level electronic structure calculations. The role of key structural units (corner and edge sharing polyhedra) in determining the network topology is investigated in terms of the underlying dynamics and the relationship to the glass transition considered.
- Industrial and Interdisciplinary Workshops