Date
Fri, 11 Dec 2009
Time
10:00 - 11:15
Location
DH 1st floor SR
Speaker
Mark Wilson
Organisation
Theoretical Chemistry, Oxford

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.

Please contact us with feedback and comments about this page. Last updated on 03 Apr 2022 01:32.