NanoMat is a laboratory for the theoretical study of materials at the atomic scale using computer simulations
We investigate structural, electronic and optical properties of materials using Density Functional Theory (DFT), Time-Dependent DFT and Many-Body Perturbation Theory (GW and Bethe-Salpeter Equation). We employ both classical and first principles molecular dynamics to simulate materials in contact with liquids. Chemical reactions are modelled using techniques such as the Nudged Elastic Band method, Activation Relaxation Technique and Metadynamics.
To perform large-scale molecular dynamics of materials we use (semi)-empirical and multi-model approaches, in particular: Semi-empirical tight binding for silicon-based systems and hybrid perovskites, and generalized SMTB-Q potentials for semiconductors and metal/semiconductor oxides; Classical molecular dynamics simulations are performed with community codes(such as LAMMPS, DL_POLY, NAMD); We generate in-house software and numerical tools to model polymers, hybrid interfaces and nanostructures, as well as for generating and interfacing to molecular dynamics codes; We use classical MD simulations and nonequilibrium statistical mechanics to model the complexity of strongly out-of-equilibrium and non-linear processes at both nano and mesoscale, such as friction and interface dissipative phenomena.
The group is active in the development of a number of software packages. We are developing interfaces between third-party codes and the open-source Quantum-ESPRESSO package for DFT simulations. Current efforts include interfacing PLUMED and ARTn with Quantum ESPRESSO, to enable the calculation of free-energy surfaces and reaction paths by means of metadynamics (PLUMED) or by means of the calculation of hessian matrix from finite differences (ARTn). In addition, a significant effort is being devoted to the development of a multi-approach and multi-scaling software to address activated processes from accurate single-event calculations to large scale manufacturing and working conditions modeling. The development involves research on topological and geometrical descriptors, event-based Kinetic Monte-Carlo off lattice, new semi-empirical potentials, semi-empirical equations for the effect of electric fields and machine learning. The group is also maintaining and using the GW-BSE plane wave code SaX.
We develop the PWSIC parallel code for structural and electronic properties calculations, implementing the variational pseudo-self-interaction correction approach (VPSIC), developed by A. Filippetti and co-workers over the years, capable of describing efficiently and accurately the properties of strongly correlated materials. We are also developing the BoltzTraP code for the calculation of transport properties according to the Bloch-Boltzmann formalism, extending the approach to energy-dependent scattering time.
We developed the first family of classical force fields for hybrid perovskites (MYP models from A. Mattoni group).
The research activity of the group is dedicated to the theoretical study of materials, surfaces, interfaces, catalytic and dissipative processes using computer simulations. The research themes covered are the following:
T1) Study of catalytic properties of metals, metal oxides and metal nanoparticles deposited on oxide surfaces using density functional theory simulations. The aim is to gain fundamental understanding of the materials properties governing the catalytic behavior. Processes of interest include redox reactions taking place in fuel cells and in electrolyzers, photoelectrochemical water splitting, heterogeneous reactions of relevance for the chemical industry such as the epoxidation of ethylene;
T2) Study of different aspects of nanomechanics, specifically underlying the nature of atomic friction and interface dissipation from nano to mesoscale. By looking at the dynamics of confined systems under shear, the study explores processes occurring in dry (e.g., graphitic) and lubricated (e.g., ionic liquid) contacts. Via MD simulations and nonequilibrium statistical mechanics, investigations address dissipative mechanisms in different kinds of systems, including manipulation and diffusion of clusters and nano-objects at surfaces, optically trapped cold ions and colloidal suspensions;
T3) Multiscale modeling of nanomaterials for photovoltaics: classical (thermodynamics, degradation, microstructure evolution) and ab initio (optical, transport, recombination properties) modeling of: hybrid perovskites, polymer-based blends, hybrid organic/oxide nanomaterials;
T4) Classical and ab initio study of electric and thermoelectric transport properties for energy-harvesting and thermoelectric applications;
T5) Ab initio study of magnetic, ferroic and strongly correlated materials, in particular oxide heterostructures, for spintronics and spin-orbitronics applications (e.g. spin-transistors, spin-torque, spin-orbit qubit devices);
T6) Study of point defects in bulk and surfaces of semiconductors and insulators, in the context of i) optical fibers and micro-electronic devices used and/or to be used in harsh environments and ii) Cultural Heritage.
