| Summary: | A new ternary compound Cu<sub>2</sub>SnTi<sub>3</sub> has been synthesized by vacuum sintering at 900 °C. The atomic structures of CaCu<sub>5</sub>- and InNi<sub>2</sub>-like Cu<sub>2</sub>SnTi<sub>3</sub> are calculated using density functional theory methods. The X-ray diffraction (XRD) analysis and selected area diffraction (SAD) patterns of the new ternary compound Cu<sub>2</sub>SnTi<sub>3</sub> are considered to verify the atomic structures of CaCu<sub>5</sub>- and InNi<sub>2</sub>-like Cu<sub>2</sub>SnTi<sub>3</sub>. The results reveal that the InNi<sub>2</sub>-like Cu<sub>2</sub>SnTi<sub>3</sub> model has the lowest total energy of −35.239 eV, representing the trigonal crystal structure. The orthorhombic crystal structure of the CaCu<sub>5</sub>-like Cu<sub>2</sub>SnTi<sub>3</sub> model has the second lowest total energy of −33.926 eV. Our theoretical X-ray diffraction peak profiles of InNi<sub>2</sub>-like (CaCu<sub>5</sub>-like) Cu<sub>2</sub>SnTi<sub>3</sub> are nearly identical to experimental one, leading to an error below 2.0% (3.0%). In addition, the hexagonal crystal structure of the CaCu<sub>5</sub>-like Cu<sub>2</sub>SnTi<sub>3</sub> model has the highest total energy of −33.094 eV. The stability of the Cu<sub>2</sub>SnTi<sub>3</sub> in terms of energy follows the order: the trigonal, orthorhombic, and hexagonal crystal structure.
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