  Accurate and predictive computations of the quantum-mechanical behavior of
many interacting electrons in realistic atomic environments are critical for
the theoretical design of materials with desired properties, and require
solving the grand-challenge problem of the many-electron Schrodinger equation.
An infinite chain of equispaced hydrogen atoms is perhaps the simplest
realistic model for a bulk material, embodying several central themes of modern
condensed matter physics and chemistry, while retaining a connection to the
paradigmatic Hubbard model. Here we report a combined application of
cutting-edge computational methods to determine the properties of the hydrogen
chain in its quantum-mechanical ground state. Varying the separation between
the nuclei leads to a rich phase diagram, including a Mott phase with quasi
long-range antiferromagnetic order, electron density dimerization with
power-law correlations, an insulator-to-metal transition and an intricate set
of intertwined magnetic orders.
