Determination of the high pressure phases of CaWO₄ by CALYPSO and X-ray diffraction studies

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• 作者：Li Wang ; Feng Ke ; Yuwei Li ; Qinglin Wang ; Cailong Liu ; Jiejuan Yan ; Hui Li ; Yonghao Han ; Yanzhang Ma and Chunxiao Gao
• 刊名：physica status solidi (b)
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：253
• 期：10
• 页码：1947-1951
• 全文大小：1584K
• ISSN：1521-3951

文摘

Theoretical and experimental methods have been conducted to study the high-pressure structures of CaWO₄, which have never been definitely determined during the past decades. By using the CALYPSO method, in addition to the previously known tetragonal scheelite structure (I4₁/a), monoclinic fergusonite structure (I2/a), and the orthorhombic structure (Cmca) predicted by previous works, we have found two other new phases of CaWO₄ at higher pressure: monoclinic P2₁/c and P2₁/m structures. Although the P2₁/c structure has the lowest energy (above 26.0 GPa), synchrotron-radiation-based X-ray diffraction measurements show that only the P2₁/m structure stably exists above 38.0 GPa. The kinetical hindrance of P2₁/c structure formation in the experiment has been attributed to its larger W-O coordination number than that of the P2₁/m structure at high pressure.