Phase transformation and crystal structure of IrTi

Composition and temperature dependence of the crystal structure of IrTi with Ti content of 46–61 at.% was investigated using high-temperature X-ray diffraction analysis. Single-point energy calculations and geometry optimization were carried out based on first-principles calculations to understand the phase stability and transformation. Using X-ray diffraction analyses, a CsCl-type B2 structure was found in Ir-61 at.% Ti at room temperature; on the other hand, an orthorhombic structure in the alloys with Ti content below 58 at.%. The atomic positions obtained through first-principles calculations suggested a distorted L10 structure refined as a new orthorhombic (Cmmm #65) structure. The orthorhombic structure changed to almost a tetragonal structure with rising temperature and finally to a distorted B2 structure above 873 K in Ir-46–58Ti alloys.