BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Memento EPFL// BEGIN:VEVENT SUMMARY:IMX Seminar Series - Dynamical materials: From atomic scale modeli ng via machine learning to experiments DTSTART:20230227T131500 DTEND:20230227T141500 DTSTAMP:20260407T141556Z UID:2ce6f4f05bf3b79a89a8f7a8bdff193e08f3f33e1be9d557b9d15f49 CATEGORIES:Conferences - Seminars DESCRIPTION:Prof. Paul Erhart\, Chalmers University of Technology Gothenbu rg\, Sweden\nThe dynamical behavior of materials at the atomic scale\, i.e .\, the motion of individual atoms\, is crucial not only for their thermod ynamic stability but directly impacts their electronic\, optical\, and tra nsport properties. Detailed insight into these dynamics is therefore funda mental for understanding and designing materials. By the very nature of th e problem the length and time scales involved are extremely short. As a re sult\, atomic scale modeling plays an important role in guiding and interp reting experimental studies\, and discovering novel phenomena and mechanis ms.\nTraditional approaches of condensed matter physics are built on pertu rbation theory and typically assume a regular (crystalline) reference latt ice. As the complexity of materials increases\, for example\, through dime nsional engineering as in the case of layered materials or by integrating organic and inorganic components such as in hybrid perovskites\, these app roaches reach their applicability limit\, both due to the explosion of the degrees of freedom and a failure of the underlying assumptions. Here\, th e combination of atomic scale simulations\, correlation function based ana lysis\, and machine learned potentials is emerging as a tool set that can lead to a paradigm shift in how we approach these questions.\nIn this pres entation\, I will show some recent work from my group that showcases the a pproach and illustrates its potential. In the first part I will focus on e xtremely anisotropic thermal conductors based on large-area van-der-Waals thin films with random interlayer rotations. They can produce among the hi ghest room-temperature thermal anisotropy ratios\, which can be used for v ery efficient thermal management in electronic devices at the nanometer sc ale. Using a combination of molecular dynamics simulations\, neuroevolutio n potentials\, and correlation function analysis\, we are able to quantita tively explain experimental data and reveal a one-dimensional glass-like t hermal transport that is concurrent with a two-dimensional crystalline tra nsport mechanism. We show that this behavior is transferable between chemi stries and identify a simple descriptor that allows one to predict the dep endence of the through-plane conductivity on the rotation angle.\nThe seco nd part of the presentation will be concerned with the atomic dynamics in perovskites\, a very large class of materials with wide-ranging applicatio ns in\, for example\, actuators\, sensors\, energy harvesting\, and optica l devices. I will show recent work concerned with the systematic construct ion of transferable and accurate models for these materials. The latter en able one to quantitatively analyze the dynamics associated with the phase transitions that are pivotal for the unique properties of perovskites. In particular\, one can show that the so-called soft modes associated with th ese transitions exhibit overdamped behavior already hundreds of Kelvin abo ve the actual transition temperature. This gives rise to a pronounced feat ure in the vibrational density of states in the zero-frequency limit\, whi ch is confirmed by quasi-elastic neutron scattering experiments. These res ults have implications for our understanding of the local structure in the se materials\, which is important for the electronic and optical propertie s.\nBio: Paul Erhart graduated from Technische Universität Darmstadt (Ger many) in 2006. Starting in 2007 he was first a post-doctoral researcher an d later a staff member at Lawrence Livermore National Laboratory in Califo rnia (USA). He joined the faculty at the Department of Physics at Chalmers in 2011. LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201 STATUS:CONFIRMED END:VEVENT END:VCALENDAR