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Aqueous inorganic salt solutions play a prominent role in both physiological and chemical experiments, and significant attention has been directed toward understanding the mechanisms underlying salt dissolution. In our effort to elucidate the hydration process of potassium chloride, we employed a comprehensive genetic algorithm to explore the structures of KCl(H2O)n (n = 1–10). A series of stable structures were identified by high-level ab initio optimization and single-point energy calculations with a zero-point energy correction. An analysis of the probability distribution of KCl(H2O)1–10 revealed that clusters with high probability at low temperatures exhibit reduced probabilities at higher temperatures, while others become more prevalent. When n = 1–9, the contact ion pair configurations or partially dissociated structures dominate in the system, and the probability distribution plot shows that the proportion of the solvent-separated ion pair (SSIP) structures of KCl(H2O)n is very small, while the SSIP configuration in KCl(H2O)10 becomes a stable structure with increasing temperature. The results from natural bond orbital analysis reveal a stronger interaction between chloride ions and water molecules. These findings provide valuable insights for a more comprehensive understanding of the intricacies of potassium chloride dissolution in water. [ABSTRACT FROM AUTHOR]

Microalloying by introducing small atoms into the interstitial sites of crystal represents an important strategy in composition design, usually enabling a leap in material performance under a tiny doping concentration. However, for the Ni–Mn-based magnetic shape memory alloys, plenty of critical scientific issues related to interstitial alloying remains ambiguous. In this work, by first-principles calculations, the occupation preferences, and the impacts and the underlying mechanisms of H, C, N, and O on magnetism, phase stability, and electronic structures of Ni2MnGa, were systemically investigated. By using a two-stage relaxation strategy, it is confirmed that all the studied interstitial atoms prefer to occupy the octahedral interstice, although the undistorted octahedral interstice possesses a smaller size than that of the tetragonal interstice. The magnetic moments of Ni and Mn around the interstitial element are highly modified, which is attributed to the decreased concentration of conduction electrons, resultant from the formation of covalent bonds between Ni and the interstitial atoms, and the revised distances between Mn–Ni(Mn) caused by the local lattice distortion. Interstitial alloying can highly tailor the phase stability and the c/a ratio of martensite. The doping of C has a great potential to destabilize the austenite owing to the reduced ferromagnetism, which is opposite to the case in steel. The atom radius of an interstitial atom may be the critical factor dominating the elastic stability of the alloyed systems. This work is expected to provide fundamental information for interstitial alloying to promote the design of advanced magnetic shape memory alloys. [ABSTRACT FROM AUTHOR]

Quartz tuning forks and qPlus-based force sensors offer an alternative approach to silicon cantilevers for investigating tip–sample interactions in scanning probe microscopy. The high-quality factor (Q) and stiffness of these sensors prevent the tip from jumping to the contact, even at sub-nanometer amplitude. The qPlus configuration enables simultaneous scanning tunneling microscopy and atomic force microscopy, achieving spatial resolution and spectroscopy at the subatomic level. However, to enable precise measurement of tip–sample interaction forces, confidence in these measurements is contingent upon the accurate calibration of the spring constant and oscillation amplitude of the sensor. Here, we have developed a method called astigmatic displacement microscopy with picometer sensitivity. [ABSTRACT FROM AUTHOR]

Valence electron concentration (e/a) dependence of phase transition temperature TM, i.e., a higher e/a leading to an elevated TM, is a well-accepted criterion for the Ni–Mn-based alloys. However, this tendency is not always obeyed by certain alloy systems, such as the Ni2Mn(Ga, Z) alloys (Z = Si, Ge, and Sn). The origin of this abnormal behavior remains uncovered. In this work, by first-principles calculations, the origin of the abnormal e/a dependence of phase stability in the Ni2MnGa1−xSix (x = 0–1) alloys is elucidated through examining the electronic structure, phonon, and magnetism. We find that the abnormal e/a dependence of phase stability intrinsically originated from the chemical composition change. The composition variation brings about a reduction of the minority-spin electronic states near the Fermi energy and the weakness of the Fermi surface nesting. Moreover, the substitution of Si for Ga leads to a decreased magnetization of austenite and an increased magnetization of martensite, which also makes a non-negligible contribution to the abnormal phase stability. The conclusions drawn for the Ni2MnGa1−xSix alloys can be well extended to understand the structural transition in other abnormal alloying systems, such as the Ni2MnGa1−xZx alloys (Z = Ge and Sn). This work clarifies the origin of the abnormal dependence of phase stability on e/a in the Ni–Mn-based alloys and provides solid knowledge for the design of advanced magnetic shape memory alloys. [ABSTRACT FROM AUTHOR]

To explore the adsorption mechanism of CH4 and H2O molecules on the surface of low-rank coal (LRC) from the microscopic point of view, the electrostatic potential and frontier orbitals of each oxygen-containing functional group (OFGs) in LRC and adsorbent molecule, the adsorption energy, and Mulliken charge layout of CH4 molecules and H2O molecules with OFGs in LRC were investigated by density functional theory (DFT) simulation method. The results of DFT calculations showed that the order of adsorption strength of CH4 molecules on different OFGs was OCH3–LRC (-9.643 kJ/mol) > C=O–LRC (−8.625 kJ/mol) > OH–LRC (−7.241 kJ/mol) > COOH–LRC (−6.194 kJ/mol), which were all smaller than that of the C–LRC model without functionalization (−10.749 kJ/mol). The presence of OFGs reduces the adsorption strength of CH4 molecules on the surface of LRC. The order of strength of adsorption of H2O molecules on different OFGs was COOH–LRC (−69.836 kJ/mol) > OH−LRC (−46.442 kJ/mol) > C=O–LRC (−42.848 kJ/mol) > OCH3–LRC (−33.079 kJ/mol), and they were all greater than that of the C–LRC model without functionalization (−32.572 kJ/mol). The presence of OFGs improves the adsorption strength of H2O molecules on the surface of LRC. Both the LRC model modified with OFGs and the non-functionalized C–LRC model showed stronger adsorption of H2O molecules compared to that of CH4 molecules. Therefore, coal seam water injection can reduce the amount of gas gushing and mitigate coal seam gas protrusion. [ABSTRACT FROM AUTHOR]

Photoreduction of graphene oxide (GO) holds great potential for developing graphene-based electrodes for high-performance supercapacitors (SCs). However, the insufficient micro-nanostructure on photoreduced GO (PRGO) restricts its electrochemical performance. Here, a hierarchically structured PRGO-based planar SC is reported by combining two-beam-laser-interference with the masking technique. The hierarchical structures improve the surface area between PRGO and electrolyte and contribute to format electric double-layer capacitors. Planar device structures with PRGO-based interdigital finger current collectors are beneficial for rapid ion diffusion paths. As a result, the hierarchically structured PRGO-based planar SC achieves an areal capacitance of 3.97 mF cm−2 at 10 mV s−1. The proposed strategy of employing hierarchically structured PRGO in the planar SC design offers a new route for manufacturing high-performance integrated energy storage devices. [ABSTRACT FROM AUTHOR]

The geometric structures and vibration frequencies of para-chlorofluorobenzene (p-ClFPh) in the first excited state of neutral and ground state of cation were investigated by resonance-enhanced multiphoton ionization and slow electron velocity-map imaging. The infrared spectrum of S0 state and absorption spectrum for S1 ← S0 transition in p-ClFPh were also recorded. Based on the one-color resonant two-photon ionization spectrum and two-color resonant two-photon ionization spectrum, we obtained the adiabatic excited-state energy of p-ClFPh as 36302±4 cm−1. In the two-color resonant two-photon ionization slow electron velocity-map imagin spectra, the accurate adiabatic ionization potential of p-ClFPh was extrapolated as 72937±8 cm−1 via threshold ionization measurement. In addition, Franck-Condon simulation was performed to help us confidently ascertain the main vibrational modes in the S1 and D0 states. Furthermore, the mixing of vibrational modes between S0 → S1 and S1 → D0 has been analyzed. [ABSTRACT FROM AUTHOR]

A high temperature superconducting (HTS) filter on double-sided Tl2Ba2Ca2Cu3O10 (Tl-2223) thin films is designed in this letter. High-quality double-sided Tl-2223 thin films are prepared on 10 x 10 x 0.5 mm³ LaAlO3 (001) substrate. The critical temperatures Tc of the films are 120 ± 1K and the critical current densities Jc are 3-4 MA/cm² at 77K for both sides. X-ray diffraction h-2h scans and rotational φ-scans prove that the films are strongly textured with the c axis perpendicular to the substrate surface. A 3-pole band-pass filter is then fabricated on the Tl-2223 thin films with 4% relative bandwidth and a center frequency of 4.0 GHz. At 77K, 100K, and 102K, the insertion loss in the passband is 0.088 dB, 0.21 dB, and 0.27 dB, respectively. These performances show that the proposed HTS filter is satisfying even when the operating temperature is above 100K, which makes it possible to work in outer space without cryogenic systems. [ABSTRACT FROM AUTHOR]

Aqueous inorganic salt solutions play a prominent role in both physiological and chemical experiments, and significant attention has been directed toward understanding the mechanisms underlying salt dissolution. In our effort to elucidate the hydration process of potassium chloride, we employed a comprehensive genetic algorithm to explore the structures of KCl(H2O)n (n = 1-10). A series of stable structures were identified by high-level ab initio optimization and single-point energy calculations with a zero-point energy correction. An analysis of the probability distribution of KCl(H2O)1-10 revealed that clusters with high probability at low temperatures exhibit reduced probabilities at higher temperatures, while others become more prevalent. When n = 1-9, the contact ion pair configurations or partially dissociated structures dominate in the system, and the probability distribution plot shows that the proportion of the solvent-separated ion pair (SSIP) structures of KCl(H2O)n is very small, while the SSIP configuration in KCl(H2O)10 becomes a stable structure with increasing temperature. The results from natural bond orbital analysis reveal a stronger interaction between chloride ions and water molecules. These findings provide valuable insights for a more comprehensive understanding of the intricacies of potassium chloride dissolution in water., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Sub-harmonic response from ultrasound contrast agent microbubbles has been demonstrated to be an effective modality for noninvasive pressure measurement. In the present study, the dependence of ultra-harmonic response on the ambient overpressure was investigated by both experimental measurements and simulations. In the measurements, the microbubbles were exposed to Gaussian pulses with varied driving frequencies and pulse lengths, at an acoustic pressure of 0.3 MPa. The amplitudes of sub- and ultra-harmonic components were measured when the ambient overpressures varied from 0-25 kPa. At the driving frequency of 1.33 MHz, the ultra-harmonic energy decreased but the sub-harmonic energy increased with the increasing overpressure; while at the driving frequency of 4 MHz, both the sub- and ultra-harmonic components showed the same tendency that the corresponding energy decreased as the overpressure was increased. A 4-MHz Gaussian pulse with 64 cycles could provide an ultra-harmonic response with both good ambient pressure sensitivity and high linearity. Furthermore, the effects of shell parameters of a microbubble on the generation of ultra- and sub-harmonic responses were discussed based on simulations using Marmottant's model. This study suggests that the ultra-harmonic response from contrast microbubbles might be applicable for noninvasive pressure measurement.