Thoretical Study on Electronic Structures and Pressure-Induced Composite Phase Transitions of Solid Oxygen

固氧电子结构与压力诱导复合相变的理论研究

基本信息

批准号：
09640433
负责人：
SUZUKI Naoshi
金额：
$ 1.92万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

From band structure calculations using full-potential (FP)-LMTO method for molecular phases of oxygen we have obtained the following important results:1. At ambient pressure the most stable state is the AF state.2. Pressure-induced insulator-metal transition occurs by band overlapping which closes the indirect energy gap. At the transition volume VィイD2MィエD2=25.98 ÅィイD13ィエD1, the magnetic moment still remains in each molecule.3. With farther decreasing the volume the magnetic moment disappears and the paramagnetic metallic phase is realized at VィイD2MィエD2=11.36 ÅィイD13ィエD1 which corresponds to the ζ-phase at 116 GPa.In order to see a possibility that the observed metallization is realized in a monatomic phase of solid oxygen we have performed band calculations of monatomic phases for the volume corresponding to that of the ζ-phase at 116 GPa(VィイD2MィエD2=11.36 ÅィイD13ィエD1). As the crystal structure we have chosen the β-Po type because it is the monatomic structure realized first under high p … More ressures in other VI-b elements. The β-Po type structure is rhombohedral and the sc, bcc and fcc structures are realized for special values of c/a of β-Po type structure. We have found that the total energy of β-Po oxygen is higher than that of the molecular ζ(monoclinic) phase obtained for the same volume. Therefore, judging from all the results of our calculations it is strongly suggested that a paramagnetic metallic state is realized in molecular solid oxygen under high pressures higher than about 100 GPa.We investigated also pressure-induced superconductivity of β-Po Se (60 Gpa < P < 150 Gpa) and of bcc Se (150 Gpa < P) in the frame work of Allen-Dynes formalism. In the bcc phase the superconducting transition temperature TィイD2cィエD2 increases considerably with decreasing pressure, and TィイD2cィエD2 reaches more than 10 K at the transition from bcc to β-Po. The origin of this remarkable increase of TィイD2cィエD2 is mainly attributed to phonon anomaly in the middle of the ГN line. In β-Po phase, on the other hand, TィイD2cィエD2 is almost pressure independent (〜5K) and there is a large jump in TィイD2cィエD2 at the transition from β-Po to bcc. Less

通过全电位(FP)-LMTO方法对氧分子相的能带结构计算，我们得到了以下重要结果：1．在环境压力下，最稳定的状态是AF状态。2．通过能带重叠发生，从而关闭了间接能隙。在过渡体积D2MD2=25.98D13D1时，磁矩仍然保留在每个分子中。 3．减小体积，磁矩消失，顺磁性金属相在 VD2MD2=11.36D13D1 处实现，对应于 116 GPa 下的 z 相。为了了解观察到的金属化在固氧单原子相中实现的可能性，我们已经对与 116 处 z 相相对应的体积进行了单原子相的能带计算GPa(ViiD2MieD2=11.36 ÅiiD13ieD1) 作为晶体结构，我们选择 β-Po 型，因为它是在其他 VI- b 元素中首先在高 p 压力下实现的单原子结构。 β-Po 型结构是菱面体且。对于β-Po型结构的c/a的特殊值，实现了sc、bcc和fcc结构，我们发现了总能量。 β-Po 氧的含量高于相同体积下获得的分子 z（单斜）相的含量，因此，从我们的所有计算结果来看，强烈表明分子固体氧在高压下实现了顺磁金属态。高于约 100 GPa。我们还在框架中研究了 β-Po Se (60 Gpa < P < 150 Gpa) 和 bcc Se (150 Gpa < P) 的压力诱导超导性在bcc相中，超导转变温度T2D2cIED2随着压力的降低而显着增加，并且在从bcc到β-Po的转变时T2D2cieD2达到10 K以上。TIID2cIED2这种显着增加的根源主要在于。另一方面，在 β-Po 相中，ГN 线中部存在声子异常。 TIID2CIED2 几乎与压力无关（~5K），并且在从 β-Po 到 bcc Less 的过渡时，TIID2CIED2 有一个很大的跳跃。