Using the two-temperature model for ultrafast matter (UFM), we compare the equation of state, pair-distribution functions $g(r)$, and phonons using the neutral pseudoatom (NPA) model with results from density-functional theory (DFT) codes and molecular-dynamics (MD) simulations for Al, Li and Na. The NPA approach uses state-dependent first-principles pseudopotentials from an `all-electron' DFT calculation with finite-$T$ XCF. It provides pair potentials, structure factors, the
`bound' and `free' states, as well as a mean ionization $\bar{Z}$ unambiguously. These are not easily accessible {\it via} DFT+MD calculations which become prohibitive for $T/T_F$ exceeding $\sim 0.6$, where $T_F$ is the Fermi temperature. Hence, both DFT+MD and NPA methods can be compared up to $\sim 8$ eV, while higher $T$ can be addressed ${\it via}$ the NPA. The high-$T_e$ phonon calculations raise the question of UFM lattice stability and surface ablation in thin UFM samples. The ablation forces in a UFM slab are used to define an "ablation time" competing with phonon formation times in thin UFM samples. Excellent agreement for all properties is found between NPA and standard DFT codes, even for Li where a strongly non-local pseudopotential is used in DFT codes. The need to use pseudopotentials appropriate to the ionization state $\bar{Z}$ is emphasized. The effect of finite-$T$ exchange-correlation functional is illustrated via its effect on the pressure and the electron-density distribution at a nucleus.
A critical assessment of models of pair-interactions and screening used in analyzing recent warm-dense matter (WDM) experiments
超快激光实验产生了越来越可靠的温密物质（WDM）数据，但依赖于根深蒂固的简单理论模型。我们重新分析了两个专题实验，避免（i）{ \it ad hoc}核心排斥模型，（ii）“汤川屏蔽”模型和（iii）电子-离子平衡假设。一个精确的，快速的密度泛函中性赝原子模型耦合到一个超网链（HNC）方程与桥项被用来计算结构因子，X射线散射，压缩性，声子和电阻率。电子结构代码用于确认计算。汤川和核心排斥模型被证明是误导。
Phonon Coupled Scattering Caused Ultralow Lattice Thermal Conductivity and Its Role in The Remarkable Thermoelectric Performance of Newly Predicted SiS2 and SiSe2 monolayers
Optical Phonon Anomaly in Bilayer Graphene with Ultrahigh Carrier Densities
采用第一性原理计算研究了不同掺杂浓度下双层石墨烯中的电子-声子耦合。所考虑的声子是长波长高能对称（S）和反对称（AS）光学模式。两者都被证明有不同的EPC诱导的声子线宽和频率偏移的费米能级$E_F$的函数。我们发现当费米能级$E_F$高于中性点约0.5 eV时，AS模与最低的两个导带有很强的耦合，产生了巨大的线宽（大于100 cm $^{-1}$）和显著的频率软化（$\sim$ 60 cm $^{-1}$）.我们的\emph{ab initio}计算结果表明，这种剧烈变化的起因是BLG中不寻常的能带结构.结果突出了能带结构对高载流子密度区BLG中EPC的影响。
Ultrafast dynamics of the low frequency shear mode in $\mathrm{1T'-MoTe_2}$
本文报道了利用飞秒泵浦-探测光谱研究半金属1 T '-MoTe 2中相干声子的动力学。在室温下的超快亚皮秒时间尺度上，在0.39 THz处观察到低频和长寿命的剪切声子模式，这是以前报道的仅在低温Td-MoTe 2相中以特征声子的形式存在。与其他光学声子模不同，剪切声子模与光激发载流子强耦合。此外，剪切模式的振幅令人惊讶地随着激发密度的增加而降低，这种现象可以归因于激发后晶格温度升高的结果。这些结果提供了有用的物理信息之间的正常的半金属1 T '和晶格反转对称性破缺II型Weyl半金属Td相的超快晶格对称性切换。
