"Can We Design Transistors One Atom at a Time?" Abstract: One of the fundamental properties of semiconductors is their ability to support electric currents under electric and magnetic fields. These properties are described by transport coefficients such as drift and Hall mobilities of electrons and holes. Over the past decade, significant progress in first-principles calculations of these coefficients have been achieved by combining density functional theory, many-body perturbation theory, and the Boltzmann transport equation. The reliability and predictive power of these methods have improved dramatically, to the point that we can now compute the carrier mobility of novel semiconductors before their experimental realization. In this talk, I will review the ab initio Boltzmann transport equation and the key approximations and computational challenges involved. I will discuss the Boltzmann solver implemented in the EPW software package, and our group's efforts to harness the latest high-performance computing hardware for transport calculations. To illustrate these advances, I will present recent work on strain-engineering the mobility of p-type GaN, and a high-throughput search for high-mobility n-type and p-type 2D channel materials for ultrascaled transistors. At the end, I will briefly introduce new computational frameworks designed to streamline and automate advanced electron-phonon and many-body calculations, including the MATCSSI cloud integration platform and the EPWpy abstraction library. MATCSSI, a collaboration between several institutions and the Texas Advanced Computing Center (TACC), provides a cloud portal with interactive Jupyter Notebook support for running many-body electronic structure calculations directly on supercomputers. EPWpy, in turn, offers a user-friendly approach to defining materials and specifying calculation workflows using an intuitive, high-level syntax. These software projects aim to lower the barriers to entry for researchers interested in first-principles calculations of transport properties and beyond, and to facilitate transparency and reproducibility in computational materials research. Bio: Feliciano Giustino is Professor of Physics at the University of Texas, Austin, and holds the Moncrief Chair in Quantum Materials Engineering. He earned his Ph.D. in Physics at the Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland, and held a post-doctoral appointment at the University of California, Berkeley. Prior to joining the University of Texas, he spent over a decade at the University of Oxford as Professor of Materials Science, and one year at Cornell University as the Mary Shepard B. Upson Visiting Professor in Engineering. He is a Fellow of the American Physical Society and a Clarivate Analytics Highly Cited Researcher, the recipient of a Leverhulme Research Leadership Award, a Moncrief Grand Challenge Award, and a Guggenheim Fellow in Physics in the Centennial Class. He serves on the Executive Editorial Board of JPhys Materials and is an Associate Editor of Journal of Computational Electronics. He specializes in electronic structure theory, high-performance computing, and the quantum design of advanced materials at the atomic scale. He is author of 180+ scientific publications and one book on density-functional theory by Oxford University Press. He initiated the open-source software project EPW, which is regularly used by research groups around the world.