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Theoretical prediction, synthesis, and crystal structure determination of new MAX phase compound V 2 SnC
Journal of Advanced Ceramics ( IF 16.9 ) Pub Date : 2020-07-27 , DOI: 10.1007/s40145-020-0391-8 Qiang Xu , Yanchun Zhou , Haiming Zhang , Anna Jiang , Quanzheng Tao , Jun Lu , Johanna Rosén , Yunhui Niu , Salvatore Grasso , Chunfeng Hu
Journal of Advanced Ceramics ( IF 16.9 ) Pub Date : 2020-07-27 , DOI: 10.1007/s40145-020-0391-8 Qiang Xu , Yanchun Zhou , Haiming Zhang , Anna Jiang , Quanzheng Tao , Jun Lu , Johanna Rosén , Yunhui Niu , Salvatore Grasso , Chunfeng Hu
Guided by the theoretical prediction, a new MAX phase V2SnC was synthesized experimentally for the first time by reaction of V, Sn, and C mixtures at 1000 °C. The chemical composition and crystal structure of this new compound were identified by the cross-check combination of first-principles calculations, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and high resolution scanning transmission electron microscopy (HR-STEM). The stacking sequence of V2C and Sn layers results in a crystal structure of space group P63/mmc. The a- and c-lattice parameters, which were determined by the Rietveld analysis of powder XRD pattern, are 0.2981(0) nm and 1.3470(6) nm, respectively. The atomic positions are V at 4f (1/3, 2/3, 0.0776(5)), Sn at 2d (2/3, 1/3, 1/4), and C at 2a (0, 0, 0). A new set of XRD data of V2SnC was also obtained. Theoretical calculations suggest that this new compound is stable with negative formation energy and formation enthalpy, satisfied Born-Huang criteria of mechanical stability, and positive phonon branches over the Brillouin zone. It also has low shear deformation resistance c44 (second-order elastic constant, cij) and shear modulus (G), positive Cauchy pressure, and low Pugh’s ratio (G/B = 0.500 < 0.571), which is regarded as a quasi-ductile MAX phase. The mechanism underpinning the quasi-ductility is associated with the presence of a metallic bond.
中文翻译:
新型MAX相化合物V 2 SnC的理论预测,合成与晶体结构确定
在理论预测的指导下,通过V,Sn和C混合物在1000°C下的反应,首次实验合成了新的MAX相V 2 SnC。通过第一性原理计算,X射线衍射(XRD),能量色散X射线光谱(EDS)和高分辨率扫描透射电子显微镜的交叉检查组合,鉴定了该新化合物的化学组成和晶体结构。 HR-STEM)。V 2 C和Sn层的堆叠顺序导致空间群P6 3 / mmc的晶体结构。在一个-和ç通过粉末XRD图的Rietveld分析确定的-晶格参数分别为0.2981(0)nm和1.3470(6)nm。原子位置是V在4f(1/3,2/3,0.0776(5)),Sn在2d(2/3,1/3,1/4),C在2a(0,0,0) 。还获得了一组新的V 2 SnC XRD数据。理论计算表明,该新化合物稳定,具有负的地层能量和地层焓,满足Born-Huang机械稳定性标准,并且在布里渊区上具有正的声子支链。它还具有较低的抗剪切变形能力c 44(二阶弹性常数c ij)和剪切模量(G),正柯西压力和低Pugh比(G / B)= 0.500 <0.571),这被视为准延性MAX相。支撑准延展性的机制与金属键的存在有关。
更新日期:2020-07-27
中文翻译:
新型MAX相化合物V 2 SnC的理论预测,合成与晶体结构确定
在理论预测的指导下,通过V,Sn和C混合物在1000°C下的反应,首次实验合成了新的MAX相V 2 SnC。通过第一性原理计算,X射线衍射(XRD),能量色散X射线光谱(EDS)和高分辨率扫描透射电子显微镜的交叉检查组合,鉴定了该新化合物的化学组成和晶体结构。 HR-STEM)。V 2 C和Sn层的堆叠顺序导致空间群P6 3 / mmc的晶体结构。在一个-和ç通过粉末XRD图的Rietveld分析确定的-晶格参数分别为0.2981(0)nm和1.3470(6)nm。原子位置是V在4f(1/3,2/3,0.0776(5)),Sn在2d(2/3,1/3,1/4),C在2a(0,0,0) 。还获得了一组新的V 2 SnC XRD数据。理论计算表明,该新化合物稳定,具有负的地层能量和地层焓,满足Born-Huang机械稳定性标准,并且在布里渊区上具有正的声子支链。它还具有较低的抗剪切变形能力c 44(二阶弹性常数c ij)和剪切模量(G),正柯西压力和低Pugh比(G / B)= 0.500 <0.571),这被视为准延性MAX相。支撑准延展性的机制与金属键的存在有关。