Featured scientist: Prof. Stefano Baroni (Scuola Internazionale Superiore di Studi Avanzati, Italy).


Prof Stefano Baroni
Prof Stefano Baroni

Many shades of blue, red and purple that we can see in the vegetable kingdom (for example, in grapes, raspberries, eggplants and flowers such as violets) are known to be generated by the presence of natural pigments called anthocyanins. However, what makes anthocyanin express in a plant a certain tone of this wide range? This intriguing basic science issue has applications of great interest to the food industry in its quest for healthier dyes from natural components.

A thorough answer will be presented in a plenary lecture of the XVIII B-MRS Meeting by Stefano Baroni, Full Professor of Condensed Matter Theoretical Physics at Scuola Internazionale Superiore di Studi Avanzati (SISSA) – an institution located in Trieste (Italy), dedicated to research and graduate studies in various areas of science. Baroni has been studying that issue, using, mainly, a computational method that considers phenomena occurring at the molecular level over several time scales.

Prof. Stefano Baroni is an internationally renowned Italian scientist who loves to invent and improve computational methods to unveil the properties of matter at the molecular scale and apply them to problems of fundamental and applicative interest. For example, Baroni is one of the principal creators of Density Functional Perturbation Theory (DFPT), a computational tool that allows the study of physical properties of materials that depend on responses to external perturbations. He is also the founder and one the main instigators of the Quantum ESPRESSO, project, one of the most popular open source softwares for quantum materials modeling and calculations at the nanoscale, and founding director of the Quantum ESPRESSO Foundation.

Stefano Baroni obtained a degree in Physics from the Università di Pisa (Italy) in 1978. After that, until 1984, he was a postdoctoral fellow at the École Polytechnique Fédérale de Lausanne (EPFL), in Switzerland. Later, he became Assistant Professor at the Department of Theoretical Physics at the Università degli Studi di Trieste until he joined SISSA in 1988. From 1994 to 1998, he was Director of CECAM, a European center for research in computational sciences and their applications, then based at the École Normale Supérieure de Lyon, in France. Thereafter, until 2003, he served as coordinator in Trieste of the Istitituto Nazione per la Fisica della Materia (INFM). From 2001 to 2008, he was Founding Director of the DEMOCRITOS national simulation center, now part of the Italian CNR. Baroni has been a visiting professor at many institutions around the world, including Université Pierre et Marie Curie (France), Princeton University (USA), University of Minnesota (USA), University of Sydney (Australia), University College London (UK).

See our mini interview with Prof. Stefano Baroni.

B-MRS Newsletter: – We´d like to know more about your scientific work. Please choose one or two of your favorite/ high-impact contributions, briefly describe them, and share the references.

For forty years my research has been motivated by the attempt to solve the fundamental equations that determine the properties of materials at the atomic scale, in the most realistic conditions practically accessible to computational science. While this effort, which I shared with many scientists more talented than me around the world, is having a tremendous impact in many and diverse technologies, as this Conference convincingly witnesses, my own motivation has been, how to say?, a bit “swotty”? Theorists like me strive to understand. Geniuses sometimes understand what they cannot teach or do not care to implement. Ordinary swots have to do, implement, and teach in order to convince themselves they have understood, and this is what I have been doing all my life, like a Renaissance craftsman. I am probably mostly known for density functional perturbation theory [https://doi.org/10.1103/RevModPhys.73.515], a technique that Paolo Giannozzi and I introduced in the late 80s [https://doi.org/10.1103/PhysRevLett.58.1861] and that is now considered the state of the art in the simulation of the vibrational properties of condensed matter. In the late 00s my colleagues and I generalised this technique to account for the dynamical phenomena that are probed in optical spectroscopies [https://doi.org/10.1103/PhysRevLett.96.113001, https://doi.org/10.1063/1.2899649]. This work provided the methodological motivation for me to enter the field of molecular spectroscopy, which eventually led me to study the color of flowers and fruits. The challenge to compute what others believe cannot be computed was also the motivation for me to enter the fascinating field of heat and charge transport in condensed matter, a senile passion I will have the privilege to report on in Symposium S of this conference on September 24 at 9:30 [https://doi.org/10.1038/nphys3509, https://doi.org/10.1038/s41598-017-15843-2, https://doi.org/10.1038/s41467-019-11572-4, https://doi.org/10.1103/PhysRevLett.122.255901, https://doi.org/10.1038/s41567-019-0562-0].

B-MRS Newsletter: – The subject of the talk aroused our curiosity. Could you tell us what led you to study these pigments? Does it have to do with industrial interest? With the search for fundamental answers? With the application of a new methodology?

As mentioned before, I was drawn to molecular spectroscopy while seeking useful applications for a new computational method that my collaborators and I had devised to deal with dynamical perturbations to quantum-mechanical systems. Ask around what would be the most important application of molecules absorbing light, and many would answer: “solar cells to produce clean, inexhaustible, energy”. So we went, and we were induced into the wrong thinking that efficient and inexpensive solar cells could be manufactured “using fruit juice” (i.e. using anthocyanins as the light-absorbing element of a photovoltaic device). It soon became clear that while the principle per se is not wrong (in fact, organic solar cells based on it are routinely assembled and used for educational purposes https://www.teachengineering.org/activities/view/uoh_organic_activity1, https://education.mrsec.wisc.edu/titanium-dioxide-raspberry-solar-cell/) the stability and efficiency of the resulting device are far too poor for industrial purposes. Meanwhile, our work attracted some attention, and I was invited to some important meetings on solar energy. On one occasion, I declined the invitation knowing that our work could not have a real impact in the field. The organisers flatteringly insisted, and I finally accepted under the condition that I would not talk of solar energy, but of the color of fruits and flowers, which had meanwhile started to arouse my curiosity. A few months later I was approached by a representative of a head-hunting company who, seeking an expert in the molecular simulation of natural dyes on behalf of a major multinational food manufacturer, had stumbled across the abstract of my talk. When I received the telephone call I thought it was a prank and I almost hung up on her. I resisted the impulse, and that was the beginning of an exciting five-years adventure in industrial research, which I never thought I would have lived and whose story I will tell in Balneário Camboriú …

For more information on this speaker and the plenary talk he will deliver at the XVIII B-MRS Meeting, click on the speaker’s photo and the title of the lecture here https://www.sbpmat.org.br/18encontro/#lectures.

Interviews with plenary speakers of the XV Brazil-MRS Meeting: Susan Sinnott (Penn State, USA).


susan sinnottComputational methods make a difference when the challenge is to develop a new material for a given technology or to adjust material properties to fit a specific application.

In the end of September, the computational materials scientist Susan Sinnott will talk about this topic of her expertise in a plenary lecture at the XV Brazil-MRS Meeting. Sinnott is Professor and Department Head of Materials Science and Engineering at Pennsylvania State University (USA). She is also the editor-in-chief of “Computational Materials Science” (Elsevier).

Susan Sinnott received her B.S. degree in Chemistry (with honors) from the University of Texas in 1987 and her doctoral degree in Physical Chemistry from Iowa State University in 1993. Then she worked as a postdoctoral associate at the U.S. Naval Research Laboratory until 1995. After that, she became a faculty member of the University of Kentucky. In 2000, she began her tenure at the University of Florida (UF). In 2012, she was named the Alumni Professor of Materials Science and director of the Cyberinfrastructure for Atomistic Materials Science at UF. In 2013, she was president of the American Vacuum Society (AVS). In 2015, she joined the Pennsylvania State University (Penn State).

Susan Sinnott is the author of more than 210 refereed journal papers and 8 book chapters. She has over 10,000 citations and an h-index of 46, according to Google Scholar.

She is a Fellow of the Materials Research Society, American Physical Society, American Ceramic Society, American Vacuum Society, and American Association for the Advancement of Science.

In the XV Brazil-MRS Meeting, Susan Sinnott will not only deliver the plenary lecture “Role of Atomic-Scale Modeling in Materials Design and Discovery”, but also take part in the roundtable “Meet the editors” to discuss scientific publication issues. Besides her position as editor-in-chief of “Computational Materials Science”, this scientist serves as associate editor, principle editor and divisional associated editor for other journals.

Here follows a short interview with the scientist.

SBPMat newsletter: – In your opinion, what are your most significant contributions to the field of materials modeling?  Explain them very briefly and, if possible, share references of resulting publications or patents, products etc.

Susan Sinnott: – My research program uses computational atomistic methods to design and investigate materials. This area has seen tremendous growth in the last two decades because of a combination of factors, including the increasing availability and low cost of fast computers, the refinement of atomistic methods, the shrinking of device dimensions, and the improved ability of experimentalists to study materials at the nanometer scale. It approaches well-established continuum level modeling (such as finite element analysis) and fluid dynamics at high length scales (100s-1000s nanometers), and overlaps with traditional physics and chemistry at small length scales (1-10 nanometers).

A major contribution from my research group is the development of inventive methods to enable the modeling of new material systems at the atomic level. In particular, my collaborators and I developed a new empirical, reactive potential for molecular dynamics simulations that allows for the modeling of heterogeneous material systems at the atomic scale, something that has traditionally only been possible with computationally intensive first principles methods such as density functional theory. This method has allowed us to investigate such otherwise intractable problems as Cu thin film growth on ZnO surfaces, and model the catalytic activity of metal clusters on oxide surfaces. These potentials have been incorporated into an open-source massively parallel molecular dynamics software developed at Sandia National Laboratory to make them available to the modeling community.

Some relevant publications are:

  • “Simulating Multifunctional Structures”, S.R. Phillpot and S.B. Sinnott, Science 325, 1634-1635 (2009).
  • “Classical atomistic simulations of surfaces and heterogeneous interfaces with charge-optimized many body potentials”, T. Liang, T-R. Shan, Y.-T. Cheng, B.D. Devine, M. Noordhoek, Y. Li, Z. Lu, S.R. Phillpot, and S.B. Sinnott, Materials Science and Engineering Reports 74, 255-279 (2013).

SBPMat newsletter: – In the abstract of your plenary lecture, you mention the concept of “materials by design”. Could you explain this idea in a few words? Today, is “materials by design” a fact or a promise?

Susan Sinnott: – The ability to design a material with desired properties a priori using computational methods has been a promise of the field of computational materials science for many years. This promise relies on designing materials that do not currently exist or with properties that are desired from compositions that are largely unknown. The day that we can input the properties desired for a given part or device into a computer and have it predict the composition and microstructure or morphology needed to produce those properties has not yet arrived but remains the ultimate goal of “materials by design” initiatives. Currently, the integration of computational and experimental approaches is more complete than ever before. This enables computational materials science methods to make predictions that can be subsequently validated, and for experimental observations to be explained. Advances depend on continued improvements in the accuracy and predictability of computational methods along with continuing improvements in the linkages of the computational results to data from experimental characterization and production methods. An integral component to the new paradigm for materials design and discovery is the production and integration of datasets from calculations, simulations, experiments, or a combination of all of these. Therefore the seamless integration of database mining and materials informatics methods with conventional experimental and computational materials science methods is required. Lastly, the materials community must reach a critical comfort level and associated understanding of the strengths and limitations of coupling these methods so that such comparisons can be made on a routine basis.

A relevant paper that discusses these ideas in more detail is:

“Material design and discovery with computational materials science”, S.B. Sinnott, Journal of Vacuum Science and Technology A 31, 050812 (2013)

SBPMat newsletter: – If you desire, leave an invitation for our readers to go to your plenary lecture at the XV Brazil-MRS Meeting.

Susan Sinnott: – I invite you to find out more at my plenary lecture at the XV Brazil-MRS Meeting.

Link to the abstract of Susan Sinnott´s plenary lecture at the XV Brazil-MRS Meeting: http://sbpmat.org.br/15encontro/speakers/abstracts/10.pdf

Plenary lectures: world-class science with social impact.


Plenary lectures: very good attendance.

The scene repeated itself daily while the event lasted: around 8.30 a.m. and 2 p.m., under the strong João Pessoa sun, lines of hundreds of participants entered the convention center and settled at the refrigerated plenary room. There, scientists with outstanding careers, attested by their H indexes of values ranging from 40 and 73, coming from England, France, Germany, Italy, Portugal and United States, shared their knowledge about matters on which they are, without a shadow of a doubt, qualified specialists.

In the event’s final plenary lecture, Robert Chang, professor at the first department of materials science in the world, at Northwestern University, resumed two subjects that had been explained by Professor Arana Varela in the memorial lecture, and which permeated almost every plenary. The first one is the essential role that materials field and, in particular, nanotechnology play in meeting, in a sustainable way, the needs and demands of humanity in healthcare, food, transportation, security and communication. The second subject is the need for collaboration to face this challenge of the 21st century.

In this context Chang, who was president of the American Materials Research Society (MRS) and founded in 1991 the International Union of Materials Research Societies (IUMRS), called upon the young Brazilians [see video below] to be part of a global network released in 2012, which promotes the interaction of young researchers in the field around these global challenges through a biennial conference and virtual platforms.

However, Chang said, the scientific collaboration among physicists, chemists, engineers, mathematicians, biologists and other researchers to develop the necessary technologies is insufficient. It is also necessary, he added, to rely on the collective, global effort from governments, companies, communities, families and individuals to deploy these technologies on peoples’ daily lives. “That requires education”, he said. For the last 20 years, the scientist has conducted the Materials World Modules Programme, which developed interactive educational material about Materials and Nanotechnology for middle and high-school students.

Nanomedicine

Luís Carlos

Portuguese professor Luís Carlos, from the University of Aveiro, brought to XIII SBPMat Meeting many examples about the applications of nanotechnology in the healthcare field that are making a difference, or may make a difference in the short-term.

Being an expert in luminescent materials, which emit light not derived from heat, the scientist showed in his plenary lecture that these materials are already of great use in medical diagnosis. Luminescent organic complexes, for example, are marketed as contrast agents for magnetic resonance imaging, and as markers for fluoroimmunoassays (used in pre- and neonatal screening and detection of proteins, viruses, antibodies, drug residues etc.).

Besides, Luís Carlos said, luminescent nanoparticles (quantum dots and nanocrystals with lanthanide ions) emerge in diagnostic techniques and also in treatments, such as the hyperthermia process. This consists in the exposition of biological tissues, usually cancerous cells, at temperatures above 45°C, causing their deaths, with minimum collateral lesions to surrounding normal tissues. With proper temperature monitoring and control, the technique can soon become popular.

For the last few years, there have been efforts to develop nanothermometers that measure intracellular temperature to service this and other applications, not only regarding Nanomedicine, but also in fields such as Microelectronics, Photonics and Microfluidics. A successful example, presented by Luís Carlos at the plenary, is the development of a nanometric platform composed by nanorods, which work as thermometers, with gold nanoparticles on its surface, which function as heaters. This is a platform that, in contrast to its small size, can bring great benefits to the improvement of the technique of hyperthermia and the study of the processes of heat transfer at the nanoscale.

LEDs and other gallium nitride devices: savings of 25% in the global electricity consumption

Sir Colin Humphreys

When the Nobel Prize in Physics was announced for three Japanese scientists whose works were essential for the development of LED white light bulbs, those who had participated in XIII SBPMat Meeting certainly remembered the plenary lecture by Sir Colin Humphreys from University of Cambridge. The material chosen by the laureates when they decided to face the challenge of creating the blue LED that would allow the white light emitting LED was gallium nitride, which was also the object of Sir Colin’s lecture.

Professor Humphreys is an expert in this material. He created and directs a research center in Cambridge devoted to gallium nitride, and he also founded two spinoff companies to commercially exploit the technology developed by his research group and manufacture LEDs grown on relatively large silicon wafers, of about 15 cm, for low cost lighting. In 2012, the spinoffs were purchased by Plessey, a manufacturer of products based on semiconductor materials with over 50 years in the market. Now these LEDs are produced by Plessey in the United Kingdom.

The gallium nitride LED bulb currently offers one of the longest shelf lives in the market – 100,000 hours of use, equivalent to 69 years without switching the bulb, against 1,000 hours of life of the incandescent light bulb and 10,000 of the fluorescent. These LEDs also provide high energetic efficiency, ranging from 100 to 200 lumens (amount of light emitted in a second) per watt of power consumed.

At the plenary lecture, Sir Colin showed that the widespread use of LEDs in lighting would result in savings of about 15% in the total electricity consumed on the planet, and thus in a substantial decrease in emissions of carbon dioxide. In fact, lighting is one of the few segments where devices with high-energy efficiency are not yet universal.

More energy can be saved, Professor Humphreys said, by replacing silicon by gallium nitride in various electronic devices. In total, Humphreys concluded, up to 25% of all electricity used in the world today could be saved, reason why, added to the other applications of gallium nitride in the healthcare field, it was enough for the British scientist to state that this manmade material is one of the most important in the world.

Organic semiconductors: OLEDs and solar cells in the spotlight

Karl Leo

Just like it happens with LEDs, the OLEDs, which are manufactured with organic materials justifying the “O” in the acronym, directly convert electricity into light and are, therefore, devices with high potential efficiency, which has been improved every year. Having each one particular advantages, LEDs and OLEDs already compete in certain markets, such as the one of displays and, in a more incipient manner in the case of organics, in the lighting market.

Along with organic solar cells, OLEDs were the focus of Karl Leo’s plenary lecture. He is a professor at the German TU Dresden and at the Saudi Arabian KAUST universities, and wrote over 550 papers with 23,000 references and 50 patent families. He is also founder of 8 spinoff companies, such as Heliatek and Novaled, which manufacture organic solar cells and OLEDs, respectively.

Professor Leo showed an important quantity of results achieved by his research groups, regarding the improvement of organic semiconductor devices. Along with his collaborators, Karl Leo has developed an extensive work about doping organic semiconductors in the transport layers of OLEDs and solar cells to increase significantly their electrical conductivity. This work resulted, for example, in obtaining white light-emitting OLEDs with energetic efficiency greater than those of fluorescent tubes.

From the left, A. Salleo, F. So, R. Faria, H. von Seggern and J. Nelson.

Karl Leo was not the only internationally renowned scientist in João Pessoa in the field of organic semiconductors. On Wednesday afternoon, a roundtable organized by Symposium D gathered four of these specialists: Alberto Salleo (Stanford University), Franky So (University of Florida), Heinz von Seggern (TU Darmstadt) and Jenny Nelson (Imperial College London). Moderated by a prominent Brazilian scientist of the field, Roberto Mendonça Faria, professor at the São Carlos Institute of Physics at University of São Paulo and SBPMat president, the session gathered dozens of participants of the meeting, of various ages, that actively participated at the debate.

The discussion was around the challenges of organic electronics, from basic research to mass production (or individual production, as pointed out by a young man of the public drawing attention to the 3D printing techniques). Various subjects of the scientific, industrial and social fields were addressed bythe panelists based on the audience’s questions. “Fortunately, there are challenges for Materials Science. Unfortunately, there are challenges for mass production,” Professor Faria summed up, resuming, somehow, one of the first lines of the round table, in which Professor Jenny Nelson lamented that the scientific community celebrated a lot more the development of a device that works than the understanding of why a particular device did not work.

Alberto Salleo

Alberto Salleo, creator of a group in Stanford that studies the relation between structure and properties on polymeric semiconductors to better understand the charge generation and transport, also delivered a plenary lecture at the event. In the lecture, Salleo cast doubt on the universality of a widespread assumption that links a high degree of crystallinity (or order) in the microstructure of these polymers to a higher charge mobility, or better performance of the devices. The scientist showed that the disorder is good for organic solar cells and cited examples of almost amorphous semiconducting polymers having similar performance to others much ordered.

Professor Salleo presented a model developed by his group to show how the charge transport in organic semiconductors works, since they are materials with heterogeneous microstructures, where disordered and ordered aggregates coexist with each other and with long polymer chains. In order to have high charge mobility, Salleo revealed, the important thing is for the aggregates to connect among themselves, which happens through the polymeric “spaghetti”.

Order, but without periodicity

Jean-Marie Dubois

The quasicrystals are far from the disorder, but also outside the traditional crystalline order. These materials were the general theme of the plenary of French researcher Jean-Marie Dubois, from Institut Jean Lamour, whose experience in this field was recognized by the scientific community through the creation of the “Jean-Marie Dubois International Award”, given every three years to research works related to quasicrystals.

First, Dubois presented an introduction to quasicrystals, materials in which the atoms are grouped into unit cells in patterns which are ordered (which may be determined by algorithms) but not periodic (never repeat themselves). Beautiful scientific and artistic images intermixed in Dubois’ presentation allowed the audience to view this aperiodic order.

The lecturer also paid homage to Dan Shechtman, who discovered quasicrystals in 1982 and, after many fights and resistance in the scientific community, eventually won the Nobel Prize in Chemistry in 2011 and generated a big shift in the vision of ordered condensed matter. Today, quasicrystalline materials are synthesized and used in various products, such as auto parts and pans, to improve their thermal conductivity, adhesion, friction, corrosion resistance etc. It is noteworthy that Dubois is among the pioneers in filing patents targeting applications of quasicrystals.

The quasicrystalline order can be observed in various types of materials. In the lecture at the XIII SBPMat Meeting, Dubois addressed, in particular, metal alloys formed by three elements (A, B and C), in which A – B and B – C form chemical bonds, while B and C repel themselves. Named by Dubois “push-pull alloys”, these materials can form very complex intermetallic compounds, with up to hundreds of atoms per unit cell. Among these, only a few can further increase their complexity to form a quasicrystalline order, which results in unique properties and open up possibilities for new applications.

Computer simulation

Roberto Dovesi

In another plenary lecture of the XIII SBPMat Meeting, supporters of computer simulation as a complement to the experimental work in the investigation of material properties, and those interested in using it, were able to hear from Professor Roberto Dovesi (Università di Torino) that this dual approach is worthwhile.

Dovesi is one of the creators of CRYSTAL, a computational tool that allows the characterization of crystalline solids from the point of view of quantum mechanics, through ab initio calculations. The first version of the program was developed from 1976 onwards and released in 1988, making CRYSTAL the first periodic code distributed publicly to the scientific community. Now in its seventh version, the program allows the study of elastic, piezoelectric, photoelastic and dielectric properties, polarizability and hyperpolarizability tensors, IR and RAMAN spectrum, structure of electronic and phononic bands, among other properties.

The Italian chemist highlighted the affordable price and high working speed of today’s computers that are suitable to run such programs. As an example, he cited a machien recently acquired by his research group for computer simulation, which, costing around 6,500 euros, is able to do long calculations in a few hours with its 64 cores. Supercomputers are not necessary, Dovesi said, and are less robust. As for software, Dovesi remarked that today the field of materials has powerful, robust, easy-to-use programs at affordable prices (a basic license of the latest version of CRYSTAL, for example, costs 600 euros.