Electronic Structure of LLM-105 Crystal under High Pressure and Low Temperature
Electronic Structure of LLM-105 Crystal under High Pressure and Low Temperature
复制标题
高压低温下LLM-105晶体的电子结构
DOI：
10.1021/acs.jpcc.0c00055
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发表时间：
2020-01-30
影响因子：
3.7
通讯作者：
Zhang, Zengming
中科院分区：
文献类型：
--
作者：
Xu, Zilong;Chen, Qiao;Zhang, Zengming
利用光致发光、吸收、拉曼光谱和密度泛函理论（DFT）研究了LLM-105晶体在高压低温下的电子结构演化。结果表明，LLM-105晶体具有较大的间接带隙可调，从室温的2.45 eV到室温的2.45 eV。1.33 34.0 GPa.在室温下，随着压力的增加，LLM-105晶体的发光强度先增强，这是由于激发波长处的吸收增加和氢键网络的增强;当压力超过9.0 GPa时，由于声子能量的增加，无辐射跃迁几率增加，导致发光强度降低。在高压冷却过程中，由于声子能量的降低，发射增强，最大发射压力可从室温下的9 GPa调节到200 K下的10.2GPa。LLM-105晶体的吸收演化表明，随着压强的增加，晶体的禁带宽度减小，在10 GPa附近发生了电子结构相变。密度泛函理论计算表明，这是由于在10 GPa左右，暴露的氧原子向氨基的电子转移发生突变，从而降低了带隙的红移率.在26.5GPa压力下发生了压致结构相变，禁带宽度突然减小。这种材料预期在高达约250 GPa的进一步压缩下被金属化。
The electronic structural evolution of LLM-105 crystal under high pressure and low temperature is investigated by photoluminescence, absorption, Raman spectra, and density functional theory (DFT) calculations. The result shows that the LLM-105 crystal possesses a large tunable indirect band gap from 2.45 eV at the ambient condition to. 1.33 eV at 34.0 GPa. With increasing pressure at room temperature, the luminescence of LLM-105 crystal first increases in intensity owing to the raised absorption at excited wavelength and the enhanced hydrogenbond network; then, over 9.0 GPa, the increase of nonradiative transition probability causes the decrease of emission intensity due to the increase of phonon energy. In the cooling process under high pressure, the emission is enhanced due to the lower phonon energy and the pressure value at maximum emission can be adjusted up to 10.2 GPa at 200 K from 9 GPa at room temperature. The absorption evolution reveals that the band gap of LLM-105 crystal decreases as the pressure increases and an electronic structure phase transition occurred at about 10 GPa. The DFT calculation indicated that it is attributed to the electronic transfer abrupt change from the exposed oxygen atom to the amino groups at about 10 GPa, which also reduces the band gap red shift rate. A pressure-induced structure phase transition occurs at 26.5 GPa indicated by a sudden decrease of band gap. This material is expected to be metalized under further compression up to about 250 GPa.