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<jats:p>We simulate the self-assembly of active colloidal molecules from binary mixtures of spherical particles using a Brownian dynamics algorithm. These particles interact via phoretic interactions, which are determined by two independently tunable parameters, surface activity and surface mobility. In systems composed of equal-size particles, we observe the formation of colloidal molecules with well-defined coordination numbers and spatial arrangement, which also display distinct dynamic functions, such as resting, translating, and rotating. By changing the size ratio to 2 : 1 between the two species, we further observe the formation of colloidal molecules with new structures arising from breaking the size symmetry. By tuning the mutual interactions between the smaller species via their surface mobility, we are able to control their spacing as well as the coordination number of the colloidal molecules. This study highlights the importance of tuning surface parameters and size asymmetry in controlling the structure and the active dynamics of colloidal molecules.</jats:p>

<jats:p>A new three-dimensional (3D) cellular model based on hinging open-cell Kelvin structure is proposed for its negative compressibility property. It is shown that this model has adjustable compressibility and does exhibit negative compressibility for some certain conformations. And further study shows that the images of compressibility are symmetrical about the certain lines, which indicates that the mechanical properties of the model in the three axial directions are interchangeable and the model itself has a certain geometric symmetry. A comparison of the Kelvin model with its anisotropic form with the dodecahedron model shows that the Kelvin model has stronger negative compressibility property in all three directions. Therefore, a new and potential method to improve negative compressibility property can be derived by selecting the system type with lower symmetry and increasing the number of geometric parameters.</jats:p>

<jats:p>The elastic anisotropy and superconductivity upon hydrostatic compression of <jats:italic>α</jats:italic>, <jats:italic>ω</jats:italic>, and <jats:italic>β</jats:italic> Hf are investigated using first-principle methods. The results of elastic anisotropies show that they increase with increasing pressure for <jats:italic>α</jats:italic> and <jats:italic>ω</jats:italic> phases, while decrease upon compression for <jats:italic>β</jats:italic> phase. The calculated superconducting transition temperatures are in excellent agreement with experiments. Electron–phonon coupling constants (<jats:italic>λ</jats:italic>) are increasing with pressure for <jats:italic>α</jats:italic> and <jats:italic>ω</jats:italic> phases, while decreasing for <jats:italic>β</jats:italic> phase. For <jats:italic>β</jats:italic> phase, the large values of <jats:italic>λ</jats:italic> are mainly due to the obvious TA1 soft mode. Under further compression, the TA1 soft vibrational mode will disappear gradually.</jats:p>

<jats:p>Thermal expansion control is always an obstructive factor and challenging in high precision engineering field. Here, the negative thermal expansion of NbF<jats:sub>3</jats:sub> and NbOF<jats:sub>2</jats:sub> was predicted by first-principles calculation with density functional theory and the quasi-harmonic approximation (QHA). We studied the total charge density, thermal vibration, and lattice dynamic to investigate the thermal expansion mechanism. We found that the presence of O induced the w bond in NbOF<jats:sub>2</jats:sub>, thus weakening the transverse vibration of F and O in NbOF<jats:sub>2</jats:sub>, compared with the case of NbF<jats:sub>3</jats:sub>. In this study, we proposed a way to tailor negative thermal expansion of metal fluorides by introducing the oxygen atoms. The present work not only predicts two NTE compounds, but also provides an insight on thermal expansion control by designing chemical bond type.</jats:p>

<jats:p>With the diversified development of the battery industry, potassium-ion batteries (PIBs) have aroused widespread interest due to their safety and high potassium reserves on earth. However, the lack of suitable anode materials limits their development and application to a certain extent. Based on first-principles calculations, we investigate the possibility of using PC<jats:sub>3</jats:sub> monolayer as the anode material for PIBs. PC<jats:sub>3</jats:sub> sheet has excellent electrical properties and meets the prerequisite of anode materials. The storage capacity of potassium is as high as 1200 mAh⋅g<jats:sup>−1</jats:sup>, which is better than many other reported potassium-ion anode materials. In addition, the outstanding advantages of PC<jats:sub>3</jats:sub> sheet, such as low diffusion barrier and moderate open-circuit voltage, make it a potential anode candidate for PIBs.</jats:p>

<jats:p>Nanographenes (NGs) can be embedded with predesigned dopants or nonhexagonal rings to tailor the electronic properties and provide ideal platforms to study the unique physical and chemical properties. Here, we report the on-surface synthesis of NBN-doped NG embedded with five- and seven-membered rings (NBN-575-NG) on Au(111) from a oligophenylene precursor preinstalled with a NBN unit and a heptagonal ring. Scanning tunneling microscopy and non-contact atomic force microscopy images elucidate the intramolecular cyclodehydrogenation and the existence of the five- and seven-membered rings. Scanning tunneling spectroscopy spectra reveal that the NBN-575-NG is a semiconductor, which agrees with the density functional theory calculation results on a freestanding NBN-575-NG with the same structure. This work provides a feasible approach for the on-surface synthesis of novel NGs containing non-hexagonal rings.</jats:p>

<jats:p>Based on <jats:italic>ab initio</jats:italic> density functional theory calculations, we demonstrate that two carbon-doped boron nitride analog of <jats:italic>α</jats:italic>-graphyne structures, B<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>N<jats:sub>3</jats:sub> and BC<jats:sub>6</jats:sub>N monolayers, are two-dimensional direct wide band gap semiconductors, and there are two inequivalent valleys in the vicinities of the vertices of their hexagonal Brillouin zones. Besides, B<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>N<jats:sub>3</jats:sub> and BC<jats:sub>6</jats:sub>N monolayers exhibit relatively high carrier mobilities, and their direct band gap feature is robust against the biaxial strain. More importantly, the energetically most favorable B<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>N<jats:sub>3</jats:sub> and BC<jats:sub>6</jats:sub>N bilayers also have direct wide band gaps, and valley polarization could be achieved by optical helicity. Finally, we show that BC<jats:sub>6</jats:sub>N monolayer might have high efficiency in photo-splitting reactions of water, and a vertical van der Waals heterostructure with a type-II energy band alignment could be designed using B<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>N<jats:sub>3</jats:sub> and BC<jats:sub>6</jats:sub>N monolayers. All the above-mentioned characteristics make B<jats:sub>3</jats:sub>C<jats:sub>2</jats:sub>N<jats:sub>3</jats:sub> and BC<jats:sub>6</jats:sub>N monolayers, bilayers, and their heterostructures recommendable candidates for applications in valleytronic devices, metal-free photocatalysts, and photovoltaic cells.</jats:p>

<jats:p>The x-ray absorption spectroscopy is a powerful tool for the detection of thermodynamic conditions and atomic structures on warm dense matter. Here, we perform first-principles molecular dynamics and x-ray absorption spectrum calculations for warm dense ammonia, which is one of the major constituents of Uranus and Neptune. The nitrogen K-shell x-ray absorption spectrum (XAS) is determined along the Hugoniot curve, and it is found that the XAS is a good indicator of the prevailing thermodynamic conditions. The atomic structures at these conditions are ascertained. Results indicate that the ammonia could dissociate to NH<jats:sub> <jats:italic>x</jats:italic> </jats:sub> (<jats:italic>x</jats:italic> = 0, 1, or 2) fragments and form nitrogen clusters, and the ratios of these products change with varying conditions. The contributions to the XAS from these products show quite different characteristics, inducing the significant change of XAS along the Hugoniot curve. Further model simulations imply that the distribution of the peak position of atomic XAS is the dominant factor affecting the total XAS.</jats:p>

<jats:p>Si-doped <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> films are fabricated through metal-organic chemical vapor deposition (MOCVD). Solar-blind ultraviolet (UV) photodetector (PD) based on the films is fabricated by standard photolithography, and the photodetection properties are investigated. The results show that the photocurrent increases to 11.2 mA under 200 μW⋅cm<jats:sup>−2</jats:sup> 254 nm illumination and ± 20 V bias, leading to photo-responsivity as high as 788 A⋅W<jats:sup>−1</jats:sup>. The Si-doped <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>-based PD is promised to perform solar-blind photodetection with high performance.</jats:p>

<jats:p>PbZr<jats:sub>0.2</jats:sub>Ti<jats:sub>0.8</jats:sub>O<jats:sub>3</jats:sub> (PZT) gate insulator with the thickness of 30 nm is grown by pulsed laser deposition (PLD) in AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs). The ferroelectric effect of PZT AlGaN/GaN MIS-HEMT is demonstrated. The polarization charge in PZT varies with different gate voltages. The equivalent polarization charge model (EPCM) is proposed for calculating the polarization charge and the concentration of two-dimensional electron gas (2DEG). The threshold voltage (<jats:italic>V</jats:italic> <jats:sub>th</jats:sub>) and output current density (<jats:italic>I</jats:italic> <jats:sub>DS</jats:sub>) can also be obtained by the EPCM. The theoretical values are in good agreement with the experimental results and the model can provide a guide for the design of the PZT MIS-HEMT. The polarization charges of PZT can be modulated by different gate-voltage stresses and the <jats:italic>V</jats:italic> <jats:sub>th</jats:sub> has a regulation range of 4.0 V. The polarization charge changes after the stress of gate voltage for several seconds. When the gate voltage is stable or changes at high frequency, the output characteristics and the current collapse of the device remain stable.</jats:p>