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首页> 外文期刊>RSC Advances >First-principles study on structural, electronic, vibrational and thermodynamic properties of Sr10(PO4)6X2 (X = F, Cl, Br)
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First-principles study on structural, electronic, vibrational and thermodynamic properties of Sr10(PO4)6X2 (X = F, Cl, Br)

机译：Sr 10 （PO 4 ） 6 X 2 （X = F，Cl，Br）

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A theoretical investigation on the structural stability, electronic, vibrational, and thermodynamic properties of the strontium apatites Sr10(PO4)6X2 (X = F, Cl, Br) is systematically conducted by the first-principles calculations. Results of cohesive energies and formation enthalpies suggest that the thermal stability of strontium apatites decreases from Sr10(PO4)6F2 (Sr-FAP) to Sr10(PO4)6Cl2 (Sr-ClAP) and further to Sr10(PO4)6Br2 (Sr-BrAP); such a tendency is also be observed with regard to the band gaps. Using linear-response approach, the detailed vibrational properties of Sr10(PO4)6X2 (X = F, Cl, Br) are obtained. According to the calculated phonon dispersions, it is concluded that strontium apatites Sr10(PO4)6X2 (X = F, Cl, Br) are dynamically stable, and the phonon behaviors are generally similar to these apatites, but most of the vibrational frequencies decrease from Sr-FAP, Sr-ClAP to Sr-BrAP. The assignment of the vibrational modes at the gamma point demonstrate that all the silent mode Bg, Bu and E2u are affected and the only optically active mode involved is the Raman active mode E2g with the replacement of larger Cl? and Br? for F?. The results calculated with the quasi-harmonic approximation (QHA) show that Sr10(PO4)6X2 (X = F, Cl, Br) exhibits similar but slightly different behaviors in terms of its thermodynamic properties, which is expected because the halogen atoms F, Cl and Br are in the same VIIA group. Significantly, all the present calculation results are satisfactory compared to the existing experimental and theoretical results.
机译：锶磷灰石Sr 10 （PO 4 的结构稳定性，电子，振动和热力学性质的理论研究small>） 6 X 2 （X = F，Cl，Br）是由原理计算。凝聚能和形成焓的结果表明，锶磷灰石的热稳定性从Sr 10 （PO 4 ） 6 F 2 （Sr-FAP）到Sr 10 （PO 4 ） 6 Cl 2 < / small>（Sr-ClAP）以及Sr 10 （PO 4 ） 6 Br 2 （Sr-BrAP）;关于带隙也观察到这种趋势。使用线性响应方法，对Sr 10 （PO 4 ） 6 X 2 （X = F，Cl，Br）。根据计算得到的声子色散，可以得出锶磷灰石Sr 10 （PO 4 ） 6 X 2 （X = F，Cl，Br）是动态稳定的，并且声子行为通常与这些相似磷灰石，但大多数振动频率从Sr-FAP，Sr-ClAP到Sr-BrAP降低。伽玛点处的振动模式分配表明，所有静音模式B g ，B u 和E 2u 受到影响，唯一涉及的光学激活模式是拉曼激活模式E 2g 较大的Cl ？ 和Br ？ 用于F ？ 。用准谐波近似（QHA）计算的结果表明Sr 10 （PO 4 ） 6 X 2 （X = F，Cl，Br）在热力学性质方面表现出相似但略有不同的行为，这是可以预期的，因为卤素原子F，Cl和Br在同一个VIIA基团中。重要的是，与现有的实验和理论结果相比，目前所有的计算结果均令人满意。

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