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\section{Introduction}  The ability to design new materials with desired properties is a key challenge. Its solution would have far-reaching implications in both fundamental science and technological applications. Whether it is a new class of semiconductors, semiconductors for the next generation of integrated circuits, superconductors for dissipationless transport of electricity, or thermoelectrics for efficient recovery of waste heat, advances in underlying materials results in advances in technology.  However, the road to saying "I want a material that has these mechanical properties combined with these optical properties with these specific thermal switching characteristics" and being able to design  a new material satisfying those properties from nothing more than the constituent elements is a long one. Why is it so difficult?  \begin{itemize}  \item define the material design challenge