Comets are named for famous astronomers like Halley and diseases for famous physicians like Parkinson. In computational quantum mechanics, fame is bestowed on methods, and the famous “Car-Parrinello method” is named for Roberto Car and Michele Parrinello. Car, who is today a theoretical chemist at Princeton University, and Parrinello, a computational chemist at ETH Zurich and USI Lugano, first joined forces in 1984 to propose a new method for calculating the movement of electrons and their nuclei, which before had to be studied independently. The Car-Parrinello molecular dynamics method became a powerful tool for studying chemical processes; it’s been called a “virtual microscope” for looking at the motion of individual atoms. The technique has had broad applications in physics and chemistry, explaining phenomena such as changes in electrical conductivity of materials in the transition from solid to liquid state. The Car-Parrinello method allows quantum chemists and physicists to understand atomic behavior in far-ranging applications; for example, analyzing the structure of the Earth’s mantle or molecular interactions within cells.
Roberto Car and Michele Parrinello make an atomic pair. Like protons and electrons, they were drawn together, and the result was extraordinary. Car, professor of chemistry and physics at Princeton University, and Parrinello, professor in computational sciences at ETH Zurich and Università della Svizzera Italiana in Switzerland, brought together their complementary expertise to do what was once considered impossible: they developed a computer algorithm that calculates the movement of electrons while taking into account that movement’s impact on the atomic nuclei.
Their method grew out of an unusual scientific partnership. Car was trained in quantum mechanics. Parrinello had a background in molecular dynamics. They met in Trieste, a small Italian city on the Adriatic Sea, which was an international center for free-wheeling theoretical physics in the 1980s. Parrinello joked that when he and Car met, they knew enough about each other’s fields to understand the problem of molecular dynamics—predicting how the motion and structural changes of a molecule over time affect its function—but not enough to understand how difficult it would be to solve it.
Both men are Italian. Car grew up in Trieste and Milan and shared his parents’ post-war optimism that society could be rebuilt on a new equitable foundation and that science would be the key to that future. But his father was diagnosed with brain cancer when Car was 11 and passed away two years later. The loss drove Car to find solace in schoolwork, especially math and physics where the fundamental laws of nature revealed themselves in mathematical terms. He earned his Ph.D. in physics from the Milan Institute of Technology in 1971 and held postdoctoral positions at the University of Milan, the Swiss Federal Institute of Technology Lausanne (EPFL), and the IBM T.J. Watson Research Center in the United States, before returning to his hometown in 1984 as a faculty member at the International School for Advanced Studies in Trieste. Car’s research focused on quantum mechanics, especially density function theory and electronic structure calculations—predicting the structural characteristics of materials at the atomic level.
Parrinello is from the opposite end of Italy, Messina, in Sicily. While in high school, Parrinello didn’t consider himself a brilliant student, but he did love math, and, like Car, saw physics as a way to apply it. In 1968, he earned his physics Ph.D. at the University of Bologna and in 1976, joined the University of Trieste. In 1980, Parrinello went on sabbatical in the U.S. at the Argonne National Laboratory to work with Aneesur Rahman, who is considered the “founding father of molecular dynamics.” Together they developed the “Parrinello-Rahman method” of molecular dynamics simulations, which analyzes structural phase transitions of solids. That work was considered foundational for the field of atomic computer simulations.
Car and Parrinello finally crossed paths in Trieste at the International School for Advanced Studies in 1984. At the time, there was no way to calculate the positions of fast-moving electrons within an atom, while taking into account the electrons’ impact on the atom’s nucleus, which moved slowly in response to the electrons’ movement. Car described himself then as a “solid state theorist.” But Parrinello brought him to see the computer’s blossoming potential in predicting more dynamic atomic arrangements.
Pursuing a new joint approach, they worked virtually round the clock for months, pushing the latest computer power to its limits. Their labor culminated in the 1985 paper, “Unified Approach for Molecular Dynamics and Density-Functional Theory.” Published in Physical Review Letters, it opened a new era for simulating matter at the atomic level and became the fifth-most-cited article in the history of the journal. In what became known as the “Car-Parrinello method,” for the first time, the motion of nuclei could be considered while at the same time solving the electrons’ position. The technique was transformative in their fields, and paved the way for quantum physicists to explain the behavior of molecules, including both biological and inorganic materials.
In the years since, Parrinello has become renowned for his interdisciplinary approach to the study of complex chemical reactions, materials science, and protein dynamics. Parrinello has developed a new method that he calls “metadynamics” for the study of rare events and the calculation of free energies. Car is celebrated for applying computational physics to simulating the atomic and energetic structure of materials. He is currently working to improve atomic approximations by adjusting time scales to account for matter state changes or chemical reactions.
Car and Parrinello’s achievements have been recognized by numerous prizes. Together they shared the 2009 Sidney Fernbach Award of the Institute of Electrical and Electronics Engineers, the 2009 Dirac Medal of the International Centre for Theoretical Physics, the 1995 Rahman Prize of the American Physical Society, and the 1990 Hewlett Packard Europhysics Prize. Separately, Parrinello was awarded the 2017 Dreyfus Prize, the 2011 Marcel Benoist Prize, and the 2001 American Chemical Society Award in Theoretical Chemistry. Car won the 2016 American Chemical Society Award in Theoretical Chemistry, the 2012 Enrico Fermi Prize of the Italian Physical Society, and the 2010 Berni J. Alder CECAM Prize in Computational Physics, among others. They are both elected members of the National Academy of Sciences. Car is a fellow of the American Physical Society and of the Royal Society of Chemistry. Parrinello is a member of the American Academy of Arts and Sciences, the British Royal Society, and the Italian Accademia Nazionale dei Lincei.
Car and Parrinello remain friends and collaborators, authoring 22 research articles together since 1985. They make a phenomenal team, figuring out how to predict molecular dynamics that are far too small to observe directly.
Information as of March 2020