Advanced classical and ab initio atomistic and molecular simulations to study processes in condensed matter chemistry and physics with applications to renewable energies and beyond

Short description of the research team

Thematic fields of interest/research areas: Advanced classical and ab initio atomistic and molecular simulations to study processes in condensed matter chemistry and physics with applications to renewable energies and beyond

Manager/head of the team: Simone Meloni

Team members: Simone Meloni. The MCS fellow will be embedded in an international network including labs leader in complementary experimental and theoretical techniques.

Research infrastructures:

Access to top level international supercomputers for multi-million equivalent core hours. Possibility to arrange a combined experimental and theoretical research involving other universities and research centres such as EPFL (CH) and CIC-Energigune (ES)

Prerequisites of the trainee researcher:

Level of education: PhD in chemistry, physics, engineering or related fields

Required working language: English, French, Italian

Further required requisites: Eager to learn and discuss about science

Contacts: Simone Meloni: Email: simone.meloni@unife.it; Phone: +39 0532 455174

Further useful information: 

The research of the group focuses on the development and application of advanced classical and ab initio molecular and atomistic simulation techniques. In particular, we focus on rare events and free energy calculations, and multi-scale modeling and their applications to materials.

METHODS
Rare events, events that happen once in a blue moon, are ubiquitous in condensed phase chemistry and physics. For example, chemical reactions, defects diffusion, protein folding, liquid intrusion/extrusion in porous media are rare events. Rare events are essentially all those processes in which the initial and final states are separated by a free energy barrier exceeding the thermal energy (kBT) at the operative conditions. In these cases, one must waiy that a (large) energy fluctuation takes place for the system to go from "reactants" to "products", which is a very unlikely – hence rare - event. In many problems of interest this happens on timescales largely exceeding the one accessible to computer simulations. We develop special techniques to "trick" simulations so that one can accelerate these processes without altering the underlying mechanism and other relevant characteristics, such as their energetics, namely their free energy barrier [1-2].

Multiscale techniques are often useful, sometimes in combination with rare event methods, when one can treat a system at different levels of accuracy. For example, in enzymes chemical reactions occur at the active site, that one needs to treat ab initio (quantum mechanics). The rest of the macromolecule serves as a functional environment selecting the species that can access the reactive "pocket" of the protein or polarizing the active site and the reactants to promote the reaction. This part of the system can be treated at a "classical" level using well established force fields. Summarizing, using multiscale techniques, quantum mechanics/molecular mechanics (QM/MM [3-4]), one can combine the best of both approaches, achieving at the same time accuracy and efficiency.

APPLICATIONS
In my group we apply the simulation techniques summarized above to materials for renewable energies, energy storage and scavenging, water harvesting, drug delivery, separation of chemicals. In particular, during the last few years we focused on halide perovskite for solar cells and optoelectronics [5-8]. Halide perovskites are 2D and 3D materials which in less than ten years allowed to develop thin films solar cells with ~25% of efficiency (single junction). The other intriguing characteristics of halide perovskite solar cells is that their fabrication is very simple; some research groups are developing techniques to deposite perovskite films equivalent to old-fashion ink printers: perovskite precursors are dripped on suitable substrates and form spontaneously upon drying.

Concerning porous materials, the hydrophobic ones can be used to store and dissipate energy, both with relevant technological applications. Indeed, one can impregnate a porous hydrophobic material with a liquid provided high enough pressure is applied. The energy that is spent in the impregnation step is returned once the action of the external force ceases or is diminished [9-12]. In these conditions, the material works as a "mechanical battery" with a high energy density, no energy dissipation and negligible environmental impact. However, some materials show a pronounced hysteresis: the extrusion pressure is lower than the intrusion one. In this case part of the energy is dissipated as heat and one can use the material for dampers, with possible applications, for example, in the aerospace industry where one has to dissipate huge amount of energy. Here the goal is i) to understand the relation between the chemical composition, structure and intrusion/extrusion characteristics of the material and optimize their design for energy storage and dissipation applications. Porous materials have a wider range of applications; for example, intrusion/extrusion can be either endo- or exo-thermic, depending on the characteristics of the system; thus, one can exploit this property to “scavenge” thermal energy dissipated in the environment. Very recently, it has been shown that intrusion/extrusion gives rise to liquid/solid contact electrification, which can be exploited to scavenge energy in energy dissipation devices. Again, nanoporous systems can be exploited for separation of chemical, e.g. in chromatography for lab or preparation applications, and for drug delivery, bringing to a slow and controlled release of drugs imbibed in the porous system under the action of a suitable stimulus.

SELECTED BIBLIOGRAPHY
[1] “Theory and methods for rare events”, Sara Bonella, Simone Meloni, Giovanni Ciccotti, The European Physical Journal B, 2012, 85, 97
[2] “Temperature accelerated Monte Carlo (TAMC): a method for sampling the free energy surface of non-analytical collective variables”, Giovanni Ciccotti, Simone Meloni, Physical Chemistry Chemical Physics, 2011, 13, 5952-5959
[3] “MiMiC: a novel framework for multiscale modeling in computational chemistry”, Jógvan Magnus Haugaard Olsen, Viacheslav Bolnykh, Simone Meloni, Emiliano Ippoliti, Martin P Bircher, Paolo Carloni, Ursula Rothlisberger, Journal of chemical theory and computation, 2019, 15, 6, 3810-3823
[4] “Extreme scalability of DFT-Based QM/MM MD simulations using MiMiC”, Viacheslav Bolnykh, Jógvan Magnus Haugaard Olsen, Simone Meloni, Martin P Bircher, Emiliano Ippoliti, Paolo Carloni, Ursula Rothlisberger, Journal of chemical theory and computation, 2019, 15, 5601-5613
[5] “Dual effect of humidity on cesium lead bromide: enhancement and degradation of perovskite films”, Diego Di Girolamo, M. Ibrahim Dar, Danilo Dini, Lorenzo Gontrani, Ruggero Caminiti, Alessandro Mattoni, Michael Graetzel and Simone Meloni, J. Mater. Chem. A, 2019,7, 12292-12302
[6] “Entropic stabilization of mixed A-cation ABX 3 metal halide perovskites for high performance perovskite solar cells”, Chenyi Yi, Jingshan Luo, Simone Meloni, Ariadni Boziki, Negar Ashari-Astani, Carole Grätzel, Shaik M Zakeeruddin, Ursula Röthlisberger, Michael Grätzel, Energy & Environmental Science 2016, 9, 656-662
[7] “Ionic polarization-induced current–voltage hysteresis in CH 3 NH 3 PbX 3 perovskite solar cells”, Simone Meloni, Thomas Moehl, Wolfgang Tress, Marius Franckevičius, Michael Saliba, Yong Hui Lee, Peng Gao, Mohammad Khaja Nazeeruddin, Shaik Mohammed Zakeeruddin, Ursula Rothlisberger, Michael Graetzel, Nature Comm. 2016, 7, 10334
[8] “Origin of unusual bandgap shift and dual emission in organic-inorganic lead halide perovskites”, M Ibrahim Dar, Gwénolé Jacopin, Simone Meloni, Alessandro Mattoni, Neha Arora, Ariadni Boziki, Shaik Mohammed Zakeeruddin, Ursula Rothlisberger, Michael Grätzel, Science Adv., 2016, 2, e1601156
[9] “Cassie–Baxter and Wenzel states on a nanostructured surface: phase diagram, metastabilities, and transition mechanism by atomistic free energy calculations”, Alberto Giacomello, Simone Meloni, Mauro Chinappi, Carlo Massimo Casciola, Langmuir, 2012, 28, 10764-10772
[10] “Metastable wetting on superhydrophobic surfaces: Continuum and atomistic views of the Cassie-Baxter–Wenzel transition”, Alberto Giacomello, Mauro Chinappi, Simone Meloni, Carlo Massimo Casciola, Phys. Rev. Lett., 2012, 109, 226102
[11] “Pore morphology determines spontaneous liquid extrusion from nanopores”, Matteo Amabili, Yaroslav Grosu, Alberto Giacomello, Simone Meloni, Abdelali Zaki, Francisco Bonilla, Abdessamad Faik, Carlo Massimo Casciola, ACS Nano, 2019, 13, 1728-1738
[12] “Self-recovery superhydrophobic surfaces: Modular design”, Emanuele Lisi, Matteo Amabili, Simone Meloni, Alberto Giacomello, Carlo Massimo Casciola, ACS Nano, 2017, 12, 359-367

Topics:

• Inorganic Chemistry
• Physical and Analytical Chemistry
• Atomic and molecular physics, optics
• Condensed matter physics