Theory of Solid-State Defects

Conclusions

John Ruskin’s attempt at a schoolgirls’ guide to crystals and their defects asserts “crystals have a limited, though a stern, code of morals; and their essential virtues are but two; the first is to be pure, and the second to be well-shaped.” Impurities and crystal shape were his only concerns. Vacancies, interstitials, antisite defects, and dislocations were still to be perceived. If Ruskin could rewrite his book today, he would have to add to his lists. Not only were glasses, polymers, composites, and multilayered crystals outside his experience, but the sins (if not the virtues) of modem materials are far more extensive than he knew when he noted “some crystals are very naughty crystals indeed.” Yet he realized the framework theory provides, and he would have recognized theory as a major and powerful complement to experiment. The added value of predictive modeling would have been inconceivable in 1865, yet it will be needed for control over materials processing and properties to approach ambitions for the next century’s materials.