MATERIALS FOR ENERGY

1. T= 700 K T= 800 K 4-fold coordination 5 -foldcoordination 6-7-fold coordination T= 900 K ComputationalMaterials Science MATERIALS FOR ENERGY CMAST (ComputationalMAterials Science & Technology) VirtualLab www.afs.enea.it/project/cmast Hydrogenstorage • Projects: • AMPEA, Joint Programme on Advanced Materials and Processes for Energy Application (EERA, European Energy ResearchAlliance) • COST Action MP1103: Nanostructured materials for solid-state hydrogen storage (FP7 European cooperation in science and technology ) • HYDROSTORE, Industria 2015 “Efficienzaenergetica” S. Giusepponi (ENEA), M. Celino (ENEA) Catalyticeffect of intermetallics in the Hydrogendesorptionmechanism at the MgH2-Mg interface The model interface withcatalyst Problem: MgH2 is a verypromising material forhydrogenstoragebuthydrogendesorptionhas low kinetic and no efficient cycling. Metalliccatalysts are usedtospeed up the desorptionprocess. Open questions: Which are the chemical and physicalprocessesthat drive, at the atomic scale, the H desorption? Whichis the mostefficientcatalysttospeed-up the desorption ? Method: Quantum moleculardynamicssimulations are usedtomodelan Mg-MgH2 interface toaccuratelyreproduce the hydrogendesorption. The interface issimulatedimposingseveralexternaltemperatures. The modelisreliablebecause the desorption temperature isfound in agreement withexperiments. Moreoverone Mg atomhasbeensubstituedby a catalyst (Fe, Pd, Ni, …) and the newdesorption temperature iscomputed. The model interface Mg MgH2 Results: Hydrogendiffusionhasbeencomputed The role of catalystshasbeenunderstood The mostefficientcatalysthasbeenselected. Mg-MgH2 interface Blu are Mg atoms. Hydrogenatomshavedifferentcoloursdepending on the distancefrom the interface. Photovoltaicapplications: anEuropeanmultiscalemodelinginfrastructure • Projects: • SOPHIA - Research Infrastructures for Solar Energy Photovoltaic Power, WP12 (FP7 INFRA-2010-1.1.22) A crystallineamorphoussiliconhasbeenheated up from the crystallinephase at low temperature till the melting and above. Rapidquench of the meltproducesanamorphousatomicconfiguration. M. Celino (ENEA) Problem: In Europeit s lacking a common computationalplatformdevotedtomodeling in the field of photovoltaicapplications. Moreoverthereis the needtogather in the sameinfrastructureall the numericalcodes and organizethem in such a way to simulate real PV systemswith the accuratness of atomic scale approaches. Open questions: Howtogatherall the numerical code in a multiscale fashion to simulate a PV system startingform the atomic scale information ? Which are the software tobedevelopedtoexchangeinformationsbetweentwodiffentmodelingscales ? Method: ENEA issharingitscomputationalfacilities, mainly the CRESCO platform, via Trans National Access mechanismtoforeingpartenersinterested in developing PV studiesbyusing high performance computingplatforms. Moreover, quantum moleculardynamics code are availabletointerestedpartners. The consortiumhaschosenHydrogenated a-Si as test case to the develop the multiscalemodelinginfrastructure. Crystalline Liquid Amorphous Quenching Melting Results: Moleculardynamics code and computationalplatform are availabletopartners Model of Hydrogenated a-Si hasbeengenerated and characterized Electronic DOS, OpticalAbsorbance and structural information are generatedas input for the highermodelingscales. Electronic DOS Opticalabsorbance Structural information Photovoltaicapplications: opticalproperties of Si(111)2x1 surfaceisomers • Projects: • CLERMONT4 project : “Exciton-polaritons: Physics and Applications “ (EU FP7, Marie Curie program PEOPLE). Band structures opticalproperties C. Violante (Tor Vergata), A. Mosca Conte (Tor Vergata), O. Pulci (Tor Vergata), F. Bechstedt (IFTO, Jena, Germany) Problem: The Si(111)2x1 is one of the most studied surfaces. Its reconstruction is described by the Pandey model with a buckling of the topmost atoms. With relation to the sign of the buckling, there are two slightly different geometric structures (isomers), conventionally named positive buckling and negative buckling. STM measurements suggest that the positive buckling isomer is the stable configuration at room temperature, but a recent work, involving STS measurements, has shown the coexistence of both the isomers, at very low temperature, for highly n-doped Si(111)2x1 specimens. Open questions: Which the stableconfiguration of the silicon (111) surface ? How the surfaceconfigurationaffects the opticalproperties of the material ? Method: Quantum calculation (DFT-LDA) tomodel the structure. GW toaccuratelycompute the electronic structure and GW todetermine the optimalpropertieswithexcitoniceffects EXP 0.47eV EXP 0.83eV The surface can befurtherfunctionalized. Results: The twoisomers are bothenergeticstablelocal minima, almost degenerate in energy and separatedbyanenergeticbarrier Differences in electronic structure and opticalproperties are evidenced: the RAS (reverse anisotropyspectroscopy) peak of the negatviebucklingisomeris more intense and redshiftedby 0.2-0.3 eVwithrespectto positive buckling. Negative buckling Positive buckling