Explore precise quantum mechanical calculations of electron interactions and dynamics in condensed matter through this 48-minute conference talk by Marco Bernardi from the California Institute of Technology. Delve into model reduction in quantum mechanics, addressing three key problems and examining the challenges in Density Functional Theory. Investigate strongly correlated materials, polaronic bonds, and structural phase transitions. Learn about recent advancements in spin phonons, the spinphonon betasalpeter equation, and defects. Gain insights into first principles methods and the Perturbo approach for model reduction in quantum mechanics.