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\section{Introduction}  The ability to design new materials with a desired set of properties is crucial to the development of new technology. The design of silicon and lithium ion lithium-ion  based materials are well known examples which led to the proliferation of consumer hand-held devices today. However, materials discovery has historically proceeded via trial and error, with intuition-guided serendipity being the most fruitful path. For example, all major classes of superconductors--from elemental mercury in 1911, to the heavy fermions, cuprates, iron-based superonductors and most recently, hydrogen sulfide in late 2014--have been discovered by chance. The dream of materials design is to leverage our theories of electronic structure, rather than ignoring them, combined with our increasing computational and storage abilities to discover new materials. Beyond its technological implications, the challenge of materials design is also one of great intellectual depth. In principle, we know all the fundamental equations needed to model the behavior of electrons and nuclei. Solving these equations is another matter, and we distinguish to classes of materials in this respect. For weakly correlated electron materials, we have a well develop theory of the excitation spectra, the Fermi liquid theory, and practical tools for their computation.