Recorded 27 March 2023. Lin Lin of the University of California, Berkeley, presents "Interacting models for twisted bilayer graphene: a quantum chemistry approach" at IPAM's Increasing the Length, Time, and Accuracy of Materials Modeling Using Exascale Computing workshop. Abstract: The nature of the correlated states in twisted bilayer graphene (TBG) at the magic angle has received intense attention in recent years. We present a numerical study of an interacting Bistritzer-MacDonald (IBM) model of TBG using a suite of methods in quantum chemistry, including Hartree-Fock, coupled cluster singles, doubles (CCSD) and perturbative triples (CCSD(T)), as well as a quantum chemistry version of the density matrix renormalization group method (QC-DMRG). Our treatment of TBG is agnostic to gauge choices, and we present a new gauge-invariant formulation to detect the spontaneous symmetry breaking in interacting models. As part of our benchmarking, we explore the impact of different schemes for removing ``double-counting'' in the IBM model. Our results suggest that cross-validation of different IBM models, and perhaps ab initio interacting models may be needed for future studies of the TBG system. Learn more online at: http://www.ipam.ucla.edu/programs/workshops/workshop-i-increasing-the-length-time-and-accuracy-of-materials-modeling-using-exascale-computing/