All models of interiors of ice bodies in the Universe rely on our knowledge of the behavior of a few simple molecules under high pressure and temperature, water being the most intriguing of them, due to its connection with life existence. Recently our team has shown that solid water under pressure can unexpectedly build up substantial amount of guest species, like ions or small gas molecules, in its lattice. The inclusion of these guest species can strongly modify the structural, dynamical, thermal and conductivity properties of ice, and promote novel exotic properties, such as the recently discovered superionicity [1]- a spectacular state of matter in which the proton diffuses and the crystalline system becomes a black hot proton super-conductor, and unexpected phenomena, such as the hyperdiffusion and hyper miscibility of methane in ice clathrates [2,3].
The existence of filled ices in extra-terrestrial bodies challenges the present description of their physics, essentially based on the properties of pure ice. Filled ices also show an enhanced gas storage and recovery capability, implying the possibility of future applications for fuel recovery and CO2 sequestration. The ultimate goal of our project is to define the range of existence of ions/gas-filled ice structures, characterize their formation, unravel their exotic properties, and tailor their future applications, by combining new groundbreaking experimental and simulation methods developed by our team, which will give access to physical properties not otherwise derivable. To this aim we combine the high pressure quasi elastic neutron scattering technique, developed by the PI, (patent n1358938 (2016)), with time resolved infrared and Raman studies, and ab-initio structural search and spectroscopy (Bachelet, Boeri). Both the PI and LB have joined la Sapienza in the last two years, after a substantial international experience. This project will help them establishing their independent research at la Sapienza.
The paramount role of water for our life, environment, and society, explains why the research on this simple system has never known a slowing down since more than a century. From cellular interior to icy planets, from hydrothermal sources to comets tails, water experiences an incredibly broad range of pressure and temperature conditions in the Universe, where it can fully disclose its unique properties. Some of these conditions have become experimentally accessible only recently. Furthermore, whenever present in Nature, water always contains ionic species or gasses dissolved in it, and this seems to be the case not only on Earth but also in extraterrestrial bodies. This notwithstanding, very little is known about the effect of those inclusions on phase diagram and the properties of water.
Within the program proposed here we put together the internationally recognized expertise of the members of our team in high pressure research, and the most innovative and groundbreaking techniques available worldwide to access the microscopic structure of doped water, as well as its exotic properties, in a broad range of thermodynamic conditions.
The characterization of the hydrogen bonded water network and of the proton and hydrogenated gas dynamics in these geophysically and environmentally relevant systems represents one missing fundamental piece of information both to realistically model planetary interiors, and to assess the viability of the use of methane and hydrogen clathrate as energy source and gas storing media.
NGHs have the ability to concentrate gas molecules closely together in the NGH crystal lattice and to yield about 160 m3 of natural gas for every m3 of NGH ¿ ideal for gas (e.g., H2) storage. Hydrogen is indeed looked upon as the next-generation clean-energy carrier; the search for an efficient, operationally convenient and cost-effective material and method for storing hydrogen reversibly has been, and is being, pursued relentlessly.
Our program has the potential of assessing the technological viability of these applications by clarifying at the molecular level the role of the gas in NGHs formation/destabilisation and by establishing the most energetically comfortable p-T conditions for NGHs stability and gas extraction.
Moreover, NGH layers are believed to exist both in comet tails and in icy body interiors, where they assume gas-filled ice structures strikingly similar to the one observed in salty-doped ices. The mobility of the gas molecules in these structures and the interplay with the water frame under these conditions are nowadays completely unknown. Our program will provide new fundamental insight to detect the presence of these systems in planetary interiors.
The scientific objectives of our project are considered among the highlights of international condensed matter research, and the expected experimental results on structural/dynamical/conductivity measurements under extreme conditions are at the forefront of the current research in the field, with a high potential interdisciplinary scientific impact (also for Planetary Science, Earth Sciences and Chemistry). We believe that the results obtained with this new kind of experimental investigation, coupled with the detailed insight coming from ab-initio and structural search computational methods, could be the object of publication in high impact interdisciplinary journals and top-class reviews in the field, as our previous publication record on correlated topics demonstrate.
The overall scientific program that we will develop has the potential to clarify some fundamental aspects of the hydrogen-bond interaction and of the quantum nature of the proton in ice, to enlighten the effects of ion and gas inclusion in ice in promoting new exotic properties, and ultimately to bring relevant outcomes for planetary modeling, and energy and hydrogen storage applications.
Concerning this last point, the increasing demand of a transition from oil and coal fuels towards environment-friendly ones has given an incredible bust to the research on gas clathrates all over the world.
Assessing the technological viability of such energy applications and implementing them require indeed a full understanding of the non-equilibrium phenomena involving gas diffusion, gas-sequestration, and guest-induced formation kinetics which we will deliver within the present project.
Italy has all the knowledge and potentialities to be one of the world leaders in these researches, and the combination of expertise and the group of scientists participating to this project are important factors for a successful development of its challenging scientific program.