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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SEMICOMPLEX (Divide and conquer ab initio semiclassical molecular dynamics for spectroscopic calculations of complex systems)

Teaser

Summary

The main idea of this project is based on an ancient military strategy. Like an ancient village succumbing to the classic Roman strategy of divide and conquer, so the complex and counterintuitive features of quantum mechanics in molecules may be uncovered through a collection of innovative semiclassical calculations. Such a powerful mathematically inspired approach paves the way to new and more accurate chemical research of large molecular systems and allows one to detect fundamental quantum mechanical properties. For instance, a close analysis of a moleculeâ€™s vibrations yields key information on its structure and constituents. Unfortunately, both theory and experiments in vibrational spectroscopy, the field of chemistry dealing with this type of question, face serious challenges when treating large molecular systems. On one hand, computer simulations entirely based on quantum dynamics are prohibitively expensive. On the other, experiments are difficult to interpret and their features hard to pin down. The computer simulations performed in this project demonstrate how spectroscopy of big molecules (like fullerene, a sixty-atom carbon buckyball, see figure) may be successfully implemented to address these problems. By combining efficient classical dynamics simulations with semiclassical mathematical tools, we recover the essential quantum features and project the original problem onto a set of smaller ones. The main beneficial outcomes for the society are in economic and technological terms. On one hand, by enlarging the field of accurate spectroscopic simulations to systems previously accessible only by experimental investigations, this project prospects for the near future the possibility to avoid expensive and sometimes even dangerous lab practices in favor of computer simulations. On the other hand, by increasing the knowledge on molecular and supra-molecular interactions, the project aims at driving the design and synthesis of new remediation materials. The main overall objectives consist in providing the scientific community with a new computational tool to solve the open scientific issue of quantum spectroscopy for large systems, and in providing experimental and industrial partners with an efficient rationalization of the physical and chemical mechanisms at the heart of the production of new materials able to improve air quality. More specifically, the SEMICOMPLEX project is devising in synergy with experimental partners nanomaterials made of titanium dioxide and conveniently modified to promote the photo-degradation of pollutants. In addition, we are developing a titanium thin film, with specific adsorbed siloxanes, that can be employ for outdoor cultural heritage preservation.

Work performed

SEMICOMPLEX activities are structured onto different levels that can be seen as concentric spheres.
At the core, there is the scientific research of the PI supported by his team, aimed to develop new theoretical chemistry methods that allow both for the correct interpretation and the prediction of spectroscopic experiments. First, the new methods are implemented into Fortran or C++ codes, and tested on simple and model systems. Then, the codes are further tested on significant real systems to be compared with well-known experimental results. Small molecules, such as water, methane and formaldehyde are our testing benchmarks, because exact calculations are available for these systems. Instead, small amino-acids, such as glycine, represent real systems where exact calculations or analytical results are not available but there are accurate experimental results to compare with. This part of the work generated internal discussions and group meetings. In particular we have invited four external speakers, whose research fields are of particular interest for the SEMICOMPLEX project and exploit their knowledge to better understand how to proceed with our work.
At the outer sphere, there is the scientific dissemination activity. This activity is mainly composed of oral or poster presentations at scientific meetings and peer-reviewed journal publications. In detail, we performed three main publications, two of them in the Journal of Chemical Physics and one in the Journal of Physical Chemistry C. In the Journal of Chemical Physics the new SEMICOMPLEX method has been presented to the theoretical chemistry community, while in the Journal of Physical Chemistry C a joint theoretical and experimental work has been presented to report validation of our theoretical speculations. As for scientific meetings, we participated at national meetings of theoretical chemists in Rome (December 2015 - National Congress of Theoretical Chemistry), in Milan (September 2016 - MolSimEng), and in Pisa (April 2017 - Molecular Properties and Computational Spectroscopy), to have the ERC project SEMICOMPLEX well known at the Italian national level. Instead, for international experts of the field, the PI organized in June 2016 a meeting in Lausanne, named â€œDifferent Routes to Quantum Molecular Dynamicsâ€. The meeting was entirely sponsored by CECAM (Centre EuropÃ©en de Calcul Atomique et MolÃ©culaire) and three SEMICOMPLEX team members presented their work to the experts of the field. The new theory and results have been positively accepted by the international community in what we think is the first step for the validation of our new methods and for further proceeding in the development of the SEMICOMPLEX project.
At a further outer sphere, we performed some outreach activities. These actives are aimed to have an impact on the ordinary people and can be divided into multimedia ones, such as the project logo and website, and in seminars and conferences. As for the latter, the SEMICOMPLEX team invited and organized at the University of Milan the lecture of Nobel medalist Prof. Martin Karplus. Prof. Karplus, who is nowadays the most eminent theoretical chemist, has been awarded the Nobel Prize in Chemistry in 2013. The choice of Prof. Karplus is motivated by the fact that a Nobel Prize winner can be easily identified by common people as the top representative in the discipline and he can reach a very broad audience. People attending the lecture were composed of colleagues at University of Milan, graduate and undergraduate students in Sciences, people from private companies and institutions related to chemistry, as well as high school students, since several high schools had been notified about the event. The Aula Magna of the University was filled with about 900 people (many of them standing). Prof. Karplus\' visit was important also for the scientific part of the project. In fact, he is considered the father of modern molecular dynamics, the branch of theoretical

Final results

The computational chemistry community is divided into static (quantum chemistry) and dynamics (molecular dynamics) communities. Within the molecular dynamics part, a very small fraction of people is devoted to quantum molecular dynamics because of the inherent difficulties, while most of the people employ classical molecular dynamics. However, classical molecular dynamics simulations do not include ubiquitous quantum mechanical effects and are heavily limited in the possibility to faithfully reproduce experiments and reliably simulate chemical, physical and biological processes. The SEMICOMPLEX project is progressing beyond the state of the art by introducing semiclassical methodologies that employ classical molecular dynamics information to reproduce quantum mechanical effects in high dimensional molecular systems. The state of the art is represented by semiclassical tools able to mimic quantum effects only for small harmonic-like molecules. We have proven that we can go beyond those systems as we can successfully tackle amino-acids and are currently dealing with big molecules like fullerene, a sixty-atom carbon buckyball. In the near future, our codes will be consolidated and available as an everyday tool to perform quantum dynamics simulations for a detailed and precise understanding of how matter is behaving. The socio-ecomomic implications will be evident in the medium-long term, when expensive and dangerous experiments will be replaced by safe and accurate computer simulations. More specifically, we are working in synergy with experimental groups at developing titania nanoparticles that can be employed for the photodegradation of pollutants. In other words, we want to use efficiently sunlight to clean the atmosphere from pollutants. Our simulations are providing the details on how pollutants are attached to titania nanoparticles and can be photo-degradaded. Also, we are devising a thin films that can be employed for outdoor cultural heritage preservation by adsorption of specific siloxanes molecules on titania.