发表机构
Joint Institute for High Temperatures（高温度联合研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究采用DFT+G₀W₀+BSE结合QMD的方法，揭示了冲击压缩下LiF的光学响应受准粒子、激子和离子温度效应的影响，其折射率与实验数据吻合度优于早期第一性原理计算，且在高压下未出现带隙闭合金属化的情况。
AI 中文摘要
我们采用DFT+G₀W₀+BSE方法研究LiF的折射率n，通过QMD纳入离子温度效应。计算了常压下的光子能量色散关系n(ω)和k(ω)，以及冲击压缩下532 nm和1550 nm波长处的n(ρ,T)，其中ρ（密度）和T（温度）协同变化。常压与压缩条件下的准粒子能带结构，以及常压下的轨道投影态密度，将光学响应与电子结构关联起来。常压下，G₀W₀得到的准粒子带隙为14.25 eV，接近实验值14.2 eV；BSE重现了12.5 eV处的主要激子特征，与观测值12.6 eV接近。因此，准粒子与激子效应对准确描述光学色散至关重要，而杂化HSE泛函无法重现该光学光谱。沿主雨贡纽曲线至140 GPa，n(ρ)与1550 nm处的冲击数据吻合度高，与532 nm处的吻合度可接受，整体表现优于早期第一性原理计算。在约110-120 GPa以上，QMD产生的结果相对于冷n(ρ)曲线出现下降，表明离子动力学可能导致偏离线性n-ρ Gladstone-Dale关系。我们还估算了QMD采样和有限k网格的不确定性，采用近期提出的判据评估了跃迁峰的展宽。带隙随压力增大，在约50 GPa附近发生Γ→L间接带隙的转变。在约1400 GPa的探索性计算得到带隙约24 eV，不利于带隙闭合的金属化。此外，还提供了基础模型的结构与弹性基准数据。
英文摘要
We investigate the refractive index $n$ of LiF using DFT+G$_0$W$_0$+BSE, with ionic-temperature effects included through QMD. We calculate photon-energy dispersions $n(ω)$ and $k(ω)$ at ambient pressure and $n(ρ,T)$ at 532 and 1550 nm under shock compression, where $ρ$ and $T$ vary together. Quasiparticle band structures at ambient and compressed conditions and the ambient-pressure orbital-projected density of states connect the optical response to the electronic structure. At ambient pressure, G$_0$W$_0$ yields a quasiparticle gap of 14.25 eV, close to the experimental 14.2 eV, while BSE reproduces the main excitonic feature at 12.5 eV, close to the observed 12.6 eV. Quasiparticle and excitonic effects are thus essential for accurate optical dispersion; the hybrid HSE functional does not reproduce the optical spectra. Along the principal Hugoniot up to 140 GPa, $n(ρ)$ agrees closely with shock data at 1550 nm and acceptably at 532 nm, and agrees better overall than earlier first-principles calculations. Above approximately 110-120 GPa, QMD produces a downturn relative to cold $n(ρ)$ curves, suggesting that ionic dynamics may contribute to deviations from the linear $n$-$ρ$ Gladstone-Dale relation. QMD-sampling and finite-k-grid uncertainties are estimated, and transition-peak broadening is assessed using a recently proposed criterion. The gap increases under pressure, with a transition to a $Γ\to\mathrm L$ indirect gap near 50 GPa. An exploratory calculation at approximately 1400 GPa finds a gap of about 24 eV, disfavoring gap-closure metallization. Structural and elastic benchmarks of the underlying models are also provided.
CommentsSubmitted to the Journal of Applied Physics; presented at XLI Fortov International Conference on Equations of State for Matter, 2026; 19 pages, 12 figures
