Quantum hardware calculations of the activation and dissociation of nitrogen on iron clusters and surfaces.

Catalytic processes are the cornerstone of chemical industry, and catalytic conversion of nitrogen to ammonia remains one of the largest industrial processes implemented. Rational design of catalysts and catalytic reactions largely depends on approximate computational chemistry methods, such as density functional theory, which, however, suffer from limited accuracy, especially for strongly-correlated materials. Rigorous methods which account for static and dynamic electron correlation, while arbitrarily accurate for small systems, are generally too expensive to be applied to modelling of catalytic cycles, due to prohibitive time and space computational complexity with respect to the size of the active space.

Adsorption of alcohols and hydrocarbons on nonstoichiometric cementite{010} surfaces.

We investigate the adsorption of several organic molecules on a nonstoichiometric {010} surface of Fe3C (cementite) by means of density functional theory calculations with van der Waals corrections. The molecules studied include methanol, ethanol, n-heptane, isooctane, benzene, toluene, cyclohexane, naphthalene, 1-methylnaphthalene and decalin. We find that methanol and ethanol chemisorb over the surface, with adsorption heats between 1.

Adsorption of atmospheric gases on cementite 010 surfaces.

We study the adsorption of a series of small molecules on the nonstoichiometric {010} surface of cementite (θ-FeC) by means of first-principles calculations. We find that CO, N, HO, and CH prefer to adsorb over iron atoms in an atop configuration. O, CO, and the OH radical prefer a configuration bridging two iron atoms and CHO adsorbs in a configuration bridging a surface iron atom and a surface carbon atom.

Impact of amorphization on the electronic properties of Zn-Ir-O systems.

We analyze the geometry and electronic structure of a series of amorphous Zn-Ir-O systems using classical molecular dynamics followed by density functional theory taking into account two different charge states of Ir (+3 and  +4). The structures obtained consist of a matrix of interconnected metal-oxygen polyhedra, with Zn adopting preferentially a coordination of 4 and Ir a mixture of coordinations between 4 and 6 that depend on the charge state of Ir and its concentration. The amorphous phases display reduced band gaps compared to crystalline ZnIr2O4 and exhibit localized states near the band edges, which harm their transparency and hole mobility.

The effect of defects and disorder on the electronic properties of ZnIr2O4.

We analyze by means of ab initio calculations the role of imperfections on the electronic structure of ZnIr2O4, ranging from point defects in the spinel phase to the fully amorphous phase. We find that interstitial defects and anion vacancies in the spinel have large formation energies, in agreement with the trends observed in other spinels. In contrast, cation vacancies and antisites have lower formation energies.

B3LYP calculations of cerium oxides.

In this paper we evaluate the performance of density functional theory with the B3LYP functional for calculations on ceria (CeO(2)) and cerium sesquioxide (Ce(2)O(3)). We demonstrate that B3LYP is able to describe CeO(2) and Ce(2)O(3) reasonably well. When compared to other functionals, B3LYP performs slightly better than the hybrid functional PBE0 for the electronic properties but slightly worse for the structural properties, although neither performs as well as LDA+U(U=6 eV) or PBE+U(U=5 eV).

Nanoporous crystal 12CaO.7Al2O3: a playground for studies of ultraviolet optical absorption of negative ions.

A novel nanoporous material 12CaO.7Al2O3 (C12A7) offers a possibility of incorporating large concentrations (>1021 cm-3) of a wide range of extraframework anions inside its nanopores. We have investigated, both experimentally and theoretically, optical absorption associated with several types of such anions, including F-, OH-, O-, O2-, O2-, and O22-, and assigned their optical absorption bands.