Antonio Tilocca: research

I use classical and first-principles computer simulations to study the properties of oxide materials and of their interfaces with (typically) aqueous environments, relevant for applications in biomedicine, energy production and catalysis. I am interested in modelling structural properties and chemical-physical processes such as surface adsorption, reactivity, ion diffusion, whose combination is crucial for the technological applications, and at the same time represents a highly complex and therefore fascinating field.

The computational methods that I use involve classical and ab-initio (Car-Parrinello) molecular dynamics. Using effective and reliable forcefields it is possible to investigate structural properties of relatively large models, as well as adsorption and diffusion on relatively long time scales. An ab-initio (based on Density Functional theory) description of interatomic forces is more suitable to study reactive processes on surfaces, where large shifts and complex rearrangements of electronic density occur on short time scales. These cannot normally be represented through empirical forcefields, due to the complexity of the substrate systems and the underlying potential energy surface. The Car-Parrinello method allows to simultaneously propagate the ionic and electronic degrees of freedom in a dynamical simulation, thus providing accurate ab-initio ionic forces "on the fly" along an MD trajectory; the explicit representation of electronic wavefunctions, inherent to the CP method, is also extremely useful to understand the electronic modifications brought about by the studied process.  

Some more details of my current and past research activity can be obtained following the hyperlinks below.

                 


Current research topics

Bioactive glasses

Titanium oxide surfaces

Maya Blue hybrid materials


Recent and past research topics

Microporous materials

DAAO enzymes

Applications of Artificial Neural Networks to Spectroscopy and Pattern Recognition






Research Funding: grants


Royal Society University Research Fellowship (2006-now):
"A more rational design of bioactive glasses based on computer modelling" (PI)

EPSRC Standard Grant EP/M004201/1 (2014-16):
"Tailoring the atomic structure of advanced sol-gel materials for regenerative medicine through high-performance computing"
(PI)

EPSRC First Grant EP/F020066/1 (2008-12):
"Alumino- and bioactive-silicate glasses as effective yttrium carriers for in situ radiotherapeutic applications"
(PI)

EPSRC Complementary Capability Challenge EP/G041156/1 (2009):
"Modelling Ion Migration in Bioactive Glasses"
(PI)

HPC-Europa Transnational Access programme (EC-funded) (2007):
"The fundamental guest-host interactions in Maya Blue pigments: DFT-CPMD calculations" (PI)


The Royal Society EPSRC EC (HPC-Europa)







Some research highlights

Hydration of a bioactive glass surface
Car-Parrinello molecular dynamics simulations illustrate the initial stages following contact of a liquid water film with the surface of a bioactive glass. This system mimics the bioglass-body fluid interface, formed in the biomedical applications of these materials. Surface silanols are formed by water dissociation at non-bridging oxygen surface sites (the oxygen atoms involved are marked green), followed by a chain of proton transfers along water molecules, which shifts the resulting local negative charge elsewhere, often close to a sodium cation. Si, P, O, Na and Ca are coloured yellow, brown, red, silver and light blue, respectively.

Read article A. Tilocca and A. N. Cormack, ACS Applied Materials & Interfaces 2009, 1, 1324.
Sodium migration mechanism in 45S5 Bioglass
The mechanism of sodium migration in low-silica alkali-alkaline earth silicate glasses was investigated through Car-Parrinelllo molecular dynamics simulations. The transport of sodium to the glass surface and its subsequent release is critical for the use of these glasses in biomedical applications. The analysis of the MD trajectory, mainly through a combination of space and time correlation functions, reveals a complex mechanism, with some common features to the migration in mixed-alkali silicate glasses and several important differences. The low site selectivity of Na cations in this glass allows them to use both Na and Ca sites in the migration process. For these low-silica compositions, the simulations suggest that due to the participation of calcium in the Na migration, the latter will not be significantly hampered by extensive mixing with less mobile Ca ions, or, in any event, the effect will be less marked than for higher-silica glasses.
The movie shows several consecutive and coordinated hops of sodium cations (highlighted in red) diffusing inside the glass. Atoms of the glass phosphosilicate network are represented as silver chains, Na and Ca cations as spheres

Read article A. Tilocca, J. Chem. Phys. 2010, 133, 014701.




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