We present a general method of constructing \textit{in-situ} pseodopotentials from first principles, all-electron, full-potential electronic structure calculations of a solid. The method is applied to bcc Na, at equilibrium volume. The essential steps of the method involve (i) calculating an all-electron Kohn-Sham eigenstate. (ii) Replacing the oscillating part of the wavefunction (inside the muffin-tin spheres) of this state, with a smooth function. (iii) Representing the smooth wavefunction in a Fourier series, and (iv) inverting the Kohn-Sham equation, to extract the pseudopotential that produces the state generated in steps (i)-(iii). It is shown that an \textit{in-situ} pseudopotential can reproduce an all-electron, full-potential eigenvalue up to the sixth significant digit. A comparison of the all-electron theory, \textit{in-situ} pseudopotential theory and the standard nonlocal pseudopotential theory demonstrates good agreement, e.g., in the energy dispersion of the 3$s$ band state of bcc Na.
The reconstruction of the complex reflection coefficient obtained by in situ Polarized Neutron Reflectometry is presented. Using the reference layer method, with a magnetic Fe layer, the phase information of the underlying Cu(001) seed layer sample structure is successfully retrieved and its scattering length density is calculated and compared with results obtained from traditional fitting. Two different reference layer approaches for retrieving the phase information are compared.
To meet growing energy demands, degradation mechanisms of energy storage devices must be better understood. As a non-destructive tool, X-ray Computed Tomography (CT) has been increasingly used by the battery community to perform $\textit{in-situ}$ experiments that can investigate dynamic phenomena. However, few have used X-ray CT to study representative battery systems over long cycle lifetimes (>100 cycles). Here, we report the $\textit{in-situ}$ CT study of Zn-Ag batteries and demonstrate the effects of current collector parasitic gassing over long-term storage and cycling. We design perform…
In this work, an optic fiber based $\textit{in situ}$ illumination system integrated into an aberration-corrected environmental transmission electron microscope (ETEM) is designed, built, characterized and applied. With this illumination system, the dynamic responses of photoactive materials to photons can be directly observed at the atomic level, and other stimuli including heating and various gases can also be applied simultaneously. Either a broadband light source or a high power laser source aiming to expedite photoreactions can be utilized, fitting different application needs. The optic f…
Using \textit{in situ} polarized neutron reflectometry, the depth resolved evolution of the magnetism and structure in a Pd/Fe/Pd trilayer thin-film is measured during growth. The initial film structure of Pd/Fe shows a small proximity induced magnetism in the underlayer and a magnetization in the Fe layer of $\approx1.6$\,$μ_{\text{B}}$ per Fe atom, less than the expected bulk value of $2.2$\,$μ_{\text{B}}$. Deposition of the Pd capping layer initially follows an island-like growth mode with subsequent coalescence. With increasing Pd deposition the Fe moment and the proximity-induced magnetis…
While the basal plane of graphene is inert, defects in it are centers of chemical activity. An attractive application of such defects is towards controlled functionalization of graphene with foreign molecules. However, the interaction of the defects with reactive environment, such as ambient, decreases the efficiency of functionalization and makes it poorly controlled. Here, we report a novel approach to generate, monitor with time resolution, and functionalize the defects $\textit{in situ}$ without ever exposing them to the ambient. The defects are generated by an energetic Argon plasma and t…
Constrained non-negative matrix factorization enabling real-time insights of $\textit{in situ}$ and high-throughput experiments
National Synchrotron Light Source II, Brookhaven National Laboratory（布鲁克海文国家实验室国家同步辐射光源II）；Center for Computational Biology, Flatiron Institute（弗拉蒂隆研究所计算生物学中心）
Quantitative modeling of \textit{in situ} x-ray reflectivity during organic molecule thin film growth
基于同步加速器的X射线反射率越来越多地被用作薄膜生长过程中表面形貌的\textit{in situ}探针，但对结果的完整解释需要对生长过程进行建模。许多模型已开发和用于这一目的，但没有详细的，比较研究，其范围和准确性存在于文献中。使用从超高温沉积的戊烷和二茚并萘（DIP）在SiO $_2$上获得的实验数据，我们比较和对比三个这样的模型，都与彼此和使用非原位原子力显微镜（AFM）的表面形貌的详细表征。这两个系统都表现出更广泛的兴趣的特殊现象：并五苯/SiO $_2$表现出从粗糙到光滑生长的快速转变。DIP/SiO $_2$，在这里采用的条件下，由于不同的基板和膜之间的粘附概率，表现出生长速率加速。在一般情况下，\textit{independent of which model is used}，我们发现从拟合\insitu X射线数据获得的表面形态与早期的实际形态之间的良好协议。一旦均方根（rms）膜粗糙度超过约1 ML，这种一致性在稍后的时间恶化。第二个观察结果是，由于层覆盖率是由反射率曲线上的一个点的演变确定的，我们发现反射率数据的最佳拟合--对应于$χ_ν^2$的最低值--不一定产生模拟和测量表面形貌之间的最佳协议。相反，模型再现数据中的所有局部极值似乎至关重要。除了显示层的形态可以从一组最小的数据中提取，这里建立的方法提供了一个基础，通过与真实系统的比较，改进多层生长模型。
Using density functional theory plus self-consistent Hubbard $U$ (DFT$+U_{sc}$) calculations, we have investigated the structural and electronic properties of the rare-earth cobaltites \textit{R}CoO$_3$ (\textit{R} = Pr -- Lu). Our calculations show the evolution of crystal and electronic structure of the insulating low-spin (LS) \textit{R}CoO$_3$ with increasing rare-earth atomic number (decreasing ionic radius), including the invariance of the Co-O bond distance ($d_{Co-O}$), the decrease of the Co-O-Co bond angle ($Θ$), and the increase of the crystal field splitting ($Δ_{CF}$) and band gap…
Large-area single-crystal monolayers of two-dimensional (2D) materials such as graphene and hexagonal boron nitride (h-BN) can be grown by chemical vapour deposition (CVD). However, the high temperatures and fast timescales at which the conversion from a gas-phase precursor to the 2D material appear, make it extremely challenging to simultaneously follow the atomic arrangements. We utilise helium atom scattering to discover and control the growth of novel 2D h-BN nanoporous phases during the CVD process. We find that prior to the formation of h-BN from the gas-phase precursor, a metastable $(3…
We studied the structural and magnetic properties of \textit{in-situ} grown iron mononitride (FeN) thin films. Initial stages of film growth were trapped utilizing synchrotron based soft x-ray absorption near edge spectroscopy (XANES) at the N $K$-edge and nuclear resonant scattering (NRS). Films were grown using dc-magnetron sputtering, separately at the experimental stations of SXAS beamline (BL01, Indus 2) and NRS beamline (P01, Petra III). It was found that the initial stages of film growth differs from the bulk of it. Ultrathin FeN films, exhibited larger energy separation between the t$_…
\textit{Ab initio} study of interacting lattice vibrations and stabilization of the $β$-phase in Ni-Ti shape-memory alloy
用于预测晶体中相变的晶格动力学方法通常评估谐波声子谱，因此在谐波近似下晶体结构不稳定的频繁和重要情况下不起作用，例如当$β$结构作为记忆合金（SMA）NiTi的高温相出现时。本文通过自洽的{ \it ab initio}晶格动力学计算（SCAILD）表明，NiTi中从预马氏体$R$到$β$相变的临界温度可以有效地精确计算，并且$β$ -相主要是不同晶格振动之间相互稳定作用的结果。
Oxide two-dimensional electron gases (2DEGs) promise high charge carrier concentrations and low-loss electronic transport in semiconductors such as BaSnO$_{3}$ (BSO). ACBN0 computations for BSO/SrNbO$_{3}$ (SNO) interfaces show Nb-4$\textit{d}$ electron injection into extended Sn-5$\textit{s}$ electronic states. The conduction band minimum consists of Sn-5$\textit{s}$ states ~1.2 eV below the Fermi level for intermediate thickness 6-unit cell BSO/6-unit cell SNO superlattices, corresponding to an electron density in BSO of ~10$^{21}$ cm$^{-3}$. Experimental studies of analogous SNO/BSO interfa…
We report the growth of thin films of the mixed valence compound YbAl$_{3}$ on MgO using molecular-beam epitaxy. Employing an aluminum buffer layer, epitaxial (001) films can be grown with sub-nm surface roughness. Using x-ray diffraction, in situ low-energy electron diffraction and aberration-corrected scanning transmission electron microscopy we establish that the films are ordered in the bulk as well as at the surface. Our films show a coherence temperature of 37 K, comparable to that reported for bulk single crystals. Photoelectron spectroscopy reveals contributions from both $\textit{f}^{…
We studied the electronic band structure of pulsed laser deposition (PLD) grown (111)-oriented SrRuO$_3$ (SRO) thin films using \textit{in situ} angle-resolved photoemission spectroscopy (ARPES) technique. We observed previously unreported, light bands with a renormalized quasiparticle effective mass of about 0.8$m_{e}$. The electron-phonon coupling underlying this mass renormalization yields a characteristic "kink" in the band dispersion. The self-energy analysis using the Einstein model suggests five optical phonon modes covering an energy range 44 to 90 meV contribute to the coupling. Besid…
