Defect chemistry is the review of position defects in imperfect crystals. These consist of vacancies, interstitial atoms or ions, trace features, electrons, or holes or every other deviation from the composition of an ideal crystal. Even Totally pure crystals consist of level defects at any temperature over absolute zero. Remedy: https://www.tumblr.com/thegemjournal/759696203354128384/understanding-the-unique-characteristics-of-yellow?source=share