Theoretical and Computational Chemistry and Materials Science

Dr. Nektarios Lathiotakis, Research Director

A main objective of our group is the exploration of materials properties using electronic structure methods aiming to offer a deeper understanding of the fundamental mechanisms behind processes and phenomena in materials’ science.  Here, we summarize a few striking examples.

We applied DFT methodology to study the effect of mechanical strain on the mechanical and vibrational properties of graphene and other 2D materials like BN and transition metal dichalcogenides (TMDs). For graphene we studied its relative stability compared with 2D allotropes that are based on Stone-Wales transformations, like pentaheptites and octa-graphene in the regime of very high uniaxial strains and estimated the strain limits for the stability of the different structures. For TMDs, in close collaboration with the experiment, we are studying the vibrational properties under mechanical load compared to the corresponding RAMAN spectra.

We introduced a simple, but accurate force field for sp² carbon systems that is built hierarchically to reproduce DFT results for graphene deformations. We tested our force field in the case of mechanical and vibrational properties of graphene, carbon nanotubes and the energetics of carbon fullerenes and we used it to study the mechanical response of graphene nanoribbons. This force field is computationally efficient, targeting large scale simulations.

We studied the electronic properties of metal oxides like SnO and SnO₂ and their dependence on Sb doping using hybrid DFT functionals and found the dependence of the band gap with doping. Our study concluded that doping does not introduce states in the gap that would invalidate the material for photovoltaic applications. We also studied the effect of H, F and Cl doping in the electronic properties of TiO₂. In addition, we studied the electronic properties of the system Sn_1-xPb_xO as well as SnO/PbO heterostructures and its band alignment.

Electron donor-acceptor systems play a crucial role in present-day photovoltaic and light emitting devices. Using time dependent DFT (TDDFT), we studied molecular donor-acceptor systems with different separations like organic molecular wires using hybrid and meta-GGA, DFT functionals. Our target was first to identify the moieties and orbitals involved in the charge-transfer process but also to assess the accuracy of empirical formulas to account for the energy differences. We considered modified Mulliken-type formulas and evaluated their accuracy. In addition, in collaboration with experimental groups, for a much larger system based on porphyrins and C₆₀, we demonstrated theoretically the charge transfer process and found agreement with experiment using semiempirical methods (PM6, ZINDO).

Key publications

Recent publications (since 2013)