Quantum Chemical Study on the Interstitial Impurities in Metals and Alloys

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First priciples molecular orbital calculations using DV-Xa method have been performed on model clusters of metals and alloys containing interstitial impurities, i.e., hydrogen, helium, carbon, nitrogen and oxygen. In iron, the sum of overlap populations over the whole cluster showed maximum values when the bond-length of H-Fe and was increased by 20% at O-site, and 10% at Tsite.respectively ; They imply these amounts of lattice distortion.Effects of solute atoms for the stability of the interstitial impurities were pursued in a similar manner.In parallel to these studies. 1) positron lifetime study of some metals and intermetallic compounds and 2) theoretical calculations of electron energy-loss near edge structures have been made.