Dynamics of growing carbon nanotube interfaces probed by machine learning-enabled molecular simulations.

Carbon nanotubes (CNTs), hollow cylinders of carbon, hold great promise for advanced technologies, provided their structure remains uniform throughout their length. Their growth takes place at high temperatures across a tube-catalyst interface. Structural defects formed during growth alter CNT properties. These defects are believed to form and heal at the tube-catalyst interface but an understanding of these mechanisms at the atomic-level is lacking. Here we present DeepCNT-22, a machine learning force field (MLFF) to drive molecular dynamics simulations through which we unveil the mechanisms of CNT formation, from nucleation to growth including defect formation and healing. We find the tube-catalyst interface to be highly dynamic, with large fluctuations in the chiral structure of the CNT-edge. This does not support continuous spiral growth as a general mechanism, instead, at these growth conditions, the growing tube edge exhibits significant configurational entropy. We demonstrate that defects form stochastically at the tube-catalyst interface, but under low growth rates and high temperatures, these heal before becoming incorporated in the tube wall, allowing CNTs to grow defect-free to seemingly unlimited lengths. These insights, not readily available through experiments, demonstrate the remarkable power of MLFF-driven simulations and fill long-standing gaps in our understanding of CNT growth mechanisms.

Realization of either physisorption or chemisorption of 2H-tetraphenylporphyrin on the Cu(111) from density functional theory.

The adsorption of organic molecules to surfaces is a central issue to achieve fully-functional molecular devices, for which porphyrins are well-studied due to their chemical stability and functional diversity. Herein, we investigate both the physical and the chemical adsorption of the free-base tetraphenylporphyrin 2H-TPP on the Cu(111) surface within the framework of density functional theory and find that the most stable physisorbed configuration is more weakly bound by -0.31 eV than the chemisorbed configuration. We use the electron localization function to investigate the difference in binding mechanisms between strong physisorption and weak chemisorption. We have computed a reaction barrier of 0.12 eV in going from physical binding to chemical bonding to the surface, and a barrier of 50 meV in going between neighboring physical binding sites. Our results support the possibility of realizing free-base porphyrins either physisorbed or chemisorbed on Cu(111) depending on the deposition procedure and experimental conditions.

Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A.

The nearby Supernova 1987A was accompanied by a burst of neutrino emission, which indicates that a compact object (a neutron star or black hole) was formed in the explosion. There has been no direct observation of this compact object. In this work, we observe the supernova remnant with JWST spectroscopy, finding narrow infrared emission lines of argon and sulfur. The line emission is spatially unresolved and blueshifted in velocity relative to the supernova rest frame. We interpret the lines as gas illuminated by a source of ionizing photons located close to the center of the expanding ejecta. Photoionization models show that the line ratios are consistent with ionization by a cooling neutron star or a pulsar wind nebula. The velocity shift could be evidence for a neutron star natal kick.

V4C3 MXene: a Type-II Nodal Line Semimetal with Potential as High-Performing Anode Material for Mg-Ion Battery.

We have used density functional theory simulations to explore the topological characteristics of a new MXene-like material, V4C3, and its oxide counterpart, assessing their potential as anode materials for Mg-ion batteries. Our research reveals that V4C3 monolayer is a topological type-II nodal line semimetal, protected by time reversal and spatial inversion symmetries. This type-II nodal line is marked by unique drumhead-like edge states that appear either inside or outside the loop circle, contingent upon the edge ending. Intriguingly, even with an increase in metallicity due to oxygen functionalization, the topological features of V4C3 remain intact. Consequently, the monolayer V4C3 has a topologically enhanced electrical conductivity that amplifies further upon oxygen functionalization. During the charging phase, a remarkable storage concentration led to a peak specific capacity of 894.73 mAh g-1 for V4C3, which only decreases to 789.33 mAh g-1 for V4C3O2. When compared to V2C, V4C3 displays a significantly lower specific capacity loss due to functionalization, demonstrating its superior electrochemical properties. Additionally, V4C3 and V4C3O2 exhibit moderate average open-circuit voltages (0.54 V for V4C3 and 0.58 V for V4C3O2) and energy barriers for intercalation migration (ranging between 0.29-0.63 eV), which are desirable for anode materials. Thus, our simulation results support V4C3 potential as an efficient anode material for Mg-ion batteries.

Physical binding energies using the electron localization function in 4-hydroxyphenylboronic acid co-crystals with aza donors.

Binding energies are traditionally simulated using cluster models by computation of each synthon for each individual co-crystal former. However, our investigation of the binding strengths using the electron localization function (ELF) reveals that these can be determined directly from the crystal supercell computations. We propose a new modeling protocol for the computation of physical binding energies directly from bulk simulations using ELF analysis. In this work, we establish a correlation between ELF values and binding energies calculated for co-crystals of 4-hydroxyphenylboronic acid (4HPBA) with four different aza donors using density functional theory with varying descriptions of dispersion. Boronic acids are gaining significant interest in the field of crystal engineering, but theoretical studies on their use in materials are still very limited. Here, we present a systematic investigation of the non-covalent interactions in experimentally realized co-crystals. Prior diffraction studies on these complexes have shown the competitive nature between the boronic acid functional group and the para-substituted phenolic group forming heteromeric interactions with aza donors. We determine the stability of the co-crystals by simulating their lattice energies, and the different dispersion descriptions show similar trends in lattice energies and lattice parameters. Our study bolsters the experimental observation of the boronic acid group as a competitive co-crystal former in addition to the well-studied phenolic group. Further research on correlating ELF values for physical binding could potentially transform this approach to a viable alternative for the computation of binding energies.

Topological Nodal Surface and Quadratic Dirac Semimetal States and van Hove Singularities in ScH3 and LuH3 Superconductors.

The coexistence of non-trivial topology and superconductivity in a material may induce a novel physical phenomenon known as topological superconductivity. Topological superconductors have been the subject of intense research, yet there are severe limitations in their application due to a lack of suitable materials. Topological nodal surface semimetals with nearly flat nodal surfaces near the Fermi level can be promising materials to achieve topological superconductivity. Here, we use first-principles calculations to examine the topological electronic characteristics of two new superconductors, ScH3 and LuH3, at both ambient and high pressures. Our studies show that both ScH3 and LuH3 have van Hove singularities, which confirms their superconductivity. Interestingly, both materials host topological nodal surface states under the protection of time reversal and spatial inversion symmetries in the absence of spin-orbit coupling (SOC). These nodal surfaces are distinguished by a pair of unique drum-head-like surface states not previously observed in nodal surface semimetals. Moreover, the nodal surfaces transform into essential spin-orbit quadratic Dirac points when SOC is included. Our findings demonstrate that ScH3 and LuH3 are good candidates to investigate the exotic properties of both nodal surface semimetals (NSSMs) and quadratic Dirac semimetal states and also provide a platform to explore the coexistence of topology and superconductivity in NSSMs with promising applications in high-speed electronics and topological quantum computing.

Exploring the Superior Anchoring Performance of the Two-Dimensional Nanosheets B2C4P2 and B3C2P3 for Lithium-Sulfur Batteries.

Potential anchoring materials in lithium-sulfur batteries help overcome the shuttle effect and achieve long-term cycling stability and high-rate efficiency. The present study investigates the two-dimensional nanosheets B2C4P2 and B3C2P3 by employing density functional theory calculations for their promise as anchoring materials. The nanosheets B2C4P2 and B3C2P3 bind polysulfides with adsorption energies in the range from -2.22 to -0.75 and -2.43 to -0.74 eV, respectively. A significant charge transfer occurs from the polysulfides, varying from -0.74 to -0.02e and -0.55 to -0.02e for B2C4P2 and B3C2P3, respectively. Upon anchoring the polysulfides, the band gap of B3C2P3 reduces, leading to enhanced electrical conductivity of the sulfur cathode. Finally, the calculated barrier energies of B2C4P2 and B3C2P3 for Li2S indicate fast diffusion of Li when recharged. These enthralling characteristics propose that the nanosheets B2C4P2 and B3C2P3 could reduce the shuttle effect in Li-S batteries and significantly improve their cycle performance, suggesting their promise as anchoring materials.

Peel-and-Stick Integration of Atomically Thin Nonlayered PtS Semiconductors for Multidimensionally Stretchable Electronic Devices.

Various near-atom-thickness two-dimensional (2D) van der Waals (vdW) crystals with unparalleled electromechanical properties have been explored for transformative devices. Currently, the availability of 2D vdW crystals is rather limited in nature as they are only obtained from certain mother crystals with intrinsically possessed layered crystallinity and anisotropic molecular bonding. Recent efforts to transform conventionally non-vdW three-dimensional (3D) crystals into ultrathin 2D-like structures have seen rapid developments to explore device building blocks of unique form factors. Herein, we explore a "peel-and-stick" approach, where a nonlayered 3D platinum sulfide (PtS) crystal, traditionally known as a cooperate mineral material, is transformed into a freestanding 2D-like membrane for electromechanical applications. The ultrathin (∼10 nm) 3D PtS films grown on large-area (>cm2) silicon dioxide/silicon (SiO2/Si) wafers are precisely "peeled" inside water retaining desired geometries via a capillary-force-driven surface wettability control. Subsequently, they are "sticked" on strain-engineered patterned substrates presenting prominent semiconducting properties, i.e., p-type transport with an optical band gap of ∼1.24 eV. A variety of mechanically deformable strain-invariant electronic devices have been demonstrated by this peel-and-stick method, including biaxially stretchable photodetectors and respiratory sensing face masks. This study offers new opportunities of 2D-like nonlayered semiconducting crystals for emerging mechanically reconfigurable and stretchable device technologies.

Oxygen-vacancy-induced magnetism in anti-perovskite topological Dirac semimetal Ba3SnO.

The thermodynamic, structural, magnetic and electronic properties of the pristine and intrinsic vacancy-defect-containing topological Dirac semimetal Ba3SnO are studied using first-principles density functional theory calculations. The thermodynamic stability of Ba3SnO has been evaluated with reference to its competing binary phases Ba2Sn, BaSn and BaO. Subsequently, valid limits of the atomic chemical potentials derived from the thermodynamic stability were used for assessing the formation of Ba, Sn and O vacancy defects in Ba3SnO under different synthesis environments. Based on the calculated defect-formation energies, we find that the charge-neutral oxygen vacancies are the most favourable type of vacancy defect under most chemical environments. The calculated electronic properties of pristine Ba3SnO show that inclusion of spin-orbit coupling in exchange-correlation potentials computed using generalized gradient approximation yields a semimetallic band structure exhibiting twin Dirac cones along the Γ-X path of the Brillouin zone. The effect of spin-polarization and spin-orbit coupling on the physical properties of intrinsic vacancy defects containing Ba3SnO has been examined in detail. Using Bader charges, electron localization function (ELF), electronic density of states (DOS) and spin density, we show that the isolated oxygen vacancy is a magnetic defect in anti-perovskite Ba3SnO. Our results show that the origin of magnetism in Ba3SnO is the accumulation of unpaired charges at the oxygen vacancy sites, which couple strongly with the 5d states of the Ba atom. Owing to the metastability observed in earlier theoretically predicted magnetic topological semimetals, the present study reveals the important role of intrinsic vacancy defects in giving rise to magnetism and also provides opportunities for engineering the electronic structure of a Dirac semimetal.

Rashba Effect and Raman Spectra of Tl2O/PtS2 Heterostructure.

The possibility to achieve charge-to-spin conversion via Rashba spin-orbit effects provides stimulating opportunities toward the development of nanoscale spintronics. Here, we use first-principles calculations to study the electronic and spintronic properties of Tl2O/PtS2 heterostructure, for which we have confirmed the dynamical stability by its positive phonon frequencies. An unexpectedly high binding energy of -0.38 eV per unit cell depicts strong interlayer interactions between Tl2O and PtS2. Interestingly, we discover Rashba spin-splittings (with a large α R value) in the valence band of Tl2O stemming from interfacial spin-orbit effects caused by PtS2. The role of van der Waals binding on the orbital rearrangements has been studied using the electron localization function and atomic orbital projections, which explains in detail the electronic dispersion near the Fermi level. Moreover, we explain the distinct band structure alignment in momentum space but separation in real space of Tl2O/PtS2 heterostructure. Since two-dimensional (2D) Tl2O still awaits experimental confirmation, we calculate, for the first time, the Raman spectra of pristine Tl2O and the Tl2O/PtS2 heterostructure and discuss peak positions corresponding to vibrational modes of the atoms. These findings offer a promising avenue to explore spin physics for potential spintronics applications via 2D heterostructures.

Definitions, indications and practice of urotherapy in children and adolescents: - A standardization document of the International Children's Continence Society (ICCS).

BACKGROUND: Urotherapy is an umbrella term for all non-surgical, non-pharmacological interventions for lower urinary tract disorders (LUTD) in children and adolescents. Urotherapy is a specialized practice, which has become mainstay therapy not only for daytime urinary incontinence, but also for nocturnal enuresis, functional constipation and fecal incontinence. The aim of urotherapy is to achieve the normalization of the micturition and bowel pattern and to prevent further functional disturbances by repeated training. It is well known that in the treatment of adult and childhood incontinence a team approach is best, where there are shared areas of expertise and also discipline-specific expertise available. AIM: We present a consensus view from a cross-professional team of experts affiliated with the International Children's Continence Society on definitions, indications and practice of urotherapy. This is a selective, non-systematic review with practical recommendations for the implementation and research on urotherapy. METHODS: The document uses the globally accepted ICCS terminology. Evidence-based literature serves as the basis, but in areas lacking in primary evidence, expert consensus is used. Before submission, a full draft was made available to all ICCS members for additional comments. RESULTS: Urotherapy uses non-pharmacological, non-surgical methods and focuses on behavioral interventions, largely based on cognitive-behavioral psychotherapy (CBT). Standard urotherapy comprises components such as provision of information, instructions, life-style advice, counselling and registration of symptoms. Specific urotherapy is tailored towards specific disorders and includes alarm treatment, biofeedback training, pelvic floor training, neurostimulation and other interventions. Fig. 1. Urotherapy is a treatment that addresses all aspects of incontinence, leading to the best clinical outcome. This includes somatic, psychosocial, and behavioral problems and quality of life. Therefore urotherapy is recommended by the ICCS as the first-line treatment for most types of LUTD. The document is intended to be clinically useful in primary, secondary and tertiary care.

Large-area 2D PtTe2/silicon vertical-junction devices with ultrafast and high-sensitivity photodetection and photovoltaic enhancement by integrating water droplets.

2D PtTe2 layers, a relatively new class of 2D crystals, have unique band structure and remarkably high electrical conductivity promising for emergent opto-electronics. This intrinsic superiority can be further leveraged toward practical device applications by merging them with mature 3D semiconductors, which has remained largely unexplored. Herein, we explored 2D/3D heterojunction devices by directly growing large-area (>cm2) 2D PtTe2 layers on Si wafers using a low-temperature CVD method and unveiled their superior opto-electrical characteristics. The devices exhibited excellent Schottky transport characteristics essential for high-performance photovoltaics and photodetection, i.e., well-balanced combination of high photodetectivity (>1013 Jones), small photo-responsiveness time (∼1 µs), high current rectification ratio (>105), and water super-hydrophobicity driven photovoltaic improvement (>300%). These performances were identified to be superior to those of previously explored 2D/3D or 2D layer-based devices with much smaller junction areas, and their underlying principles were confirmed by DFT calculations.

Superior Anchoring of Sodium Polysulfides to the Polar C2N 2D Material: A Potential Electrode Enhancer in Sodium-Sulfur Batteries.

Despite the high theoretical specific energy in rechargeable sodium-sulfur batteries, the shuttle effect severely hampers its capacity and reversibility, which could be overcome by introducing an anchoring material. We, herein, use first-principles calculations to study the low-cost, easily synthesized, environmentally friendly, and stable two-dimensional polar nitrogenated holey graphene (C2N) and nonpolar polyaniline (C3N) to investigate their performance as anchoring materials and the mechanism behind the binding to identify the best candidate to improve the performance of sodium-sulfur batteries. We gain insight into the interaction, including the lowest-energy configurations, binding energies, binding nature, charge transfer, and electronic properties. Sodium primarily contributes to binding with the nanosheets, which is in accordance with their characteristics as anchoring materials. Sodium polysulfides (NaPSs) and the S8 cluster adsorb at the pores of C2N, where there are six electron lone pairs, one for each N atom. The polar C2N binds the NaPSs much strongly than the nonpolar C3N. In contrast to C3N, the charge population substantially modifies by adsorbing NaPSs on C2N, with a substantial charge transfer from the sulfur atoms. The calculated work function of 6.04 eV for pristine C2N, comparable with the previously reported values, decreases on adsorption of the NaPSs formed from battery discharging. We suggest that the inclusion of C2N into sulfur electrodes could also improve their issue with poor conductivity.

Repetitive non-thermal melting as a timing monitor for femtosecond pump/probe X-ray experiments.

Time-resolved optical pump/X-ray probe experiments are often used to study structural dynamics. To ensure high temporal resolution, it is necessary to monitor the timing between the X-ray pulses and the laser pulses. The transition from a crystalline solid material to a disordered state in a non-thermal melting process can be used as a reliable timing monitor. We have performed a study of the non-thermal melting of InSb in single-shot mode, where we varied the sample temperature in order to determine the conditions required for repetitive melting. We show how experimental conditions affect the feasibility of such a timing tool.

Role of Thermal Equilibrium Dynamics in Atomic Motion during Nonthermal Laser-Induced Melting.

This study shows that initial atomic velocities as given by thermodynamics play an important role in the dynamics of phase transitions. We tracked the atomic motion during nonthermal laser-induced melting of InSb at different initial temperatures. The ultrafast atomic motion following bond breaking can in general be governed by two mechanisms: the random velocity of each atom at the time of bond breaking (inertial model), and the forces acting on the atoms after bond breaking. The melting dynamics was found to follow the inertial model over a wide temperature range.

Distinguishing between chemical bonding and physical binding using electron localization function (ELF).

To distinguish between chemical bonding and physical binding is usually simple. They differ, in the normal case, in both interaction strength (binding energy) and interaction length (structure). However, chemical bonding can be weak (e.g. in some metallic bonding) and physical binding can be strong (e.g. due to permanent electrostatic moments, hydrogen binding, etc) making differentiation non-trivial. But since these are shared-electron or unshared-electron interactions, respectively, it is in principle possible to distinguish the type of interaction by analyzing the electron density around the interaction point(s)/interface. After all, the former should be a contact while the latter should be a tunneling barrier. Here, we investigate within the framework of density functional theory typical molecules and crystals to show the behaviour of the electron localization function (ELF) in different shared-electron interactions, such as chemical (covalent) and metallic bonding and compare to unshared-electron interactions typical for physical binding, such as ionic, hydrogen and Keesom, dispersion (van der Waals) binding and attempt to categorise them only by the ELF and the electron population in the interaction region. It is found that the ELF method is not only useful for the characterization of covalent bonds but a lot of information can be extracted also for weaker types of binding. Furthermore, the charge integration over the interaction region(s) and tracing the ELF profile can reveal the strength of the bonding/binding ranging from the triple bonds to weak dispersion.

Wafer-Scale Growth of 2D PtTe2 with Layer Orientation Tunable High Electrical Conductivity and Superior Hydrophobicity.

Platinum ditelluride (PtTe2) is an emerging semimetallic two-dimensional (2D) transition-metal dichalcogenide (TMDC) crystal with intriguing band structures and unusual topological properties. Despite much devoted efforts, scalable and controllable synthesis of large-area 2D PtTe2 with well-defined layer orientation has not been established, leaving its projected structure-property relationship largely unclarified. Herein, we report a scalable low-temperature growth of 2D PtTe2 layers on an area greater than a few square centimeters by reacting Pt thin films of controlled thickness with vaporized tellurium at 400 °C. We systematically investigated their thickness-dependent 2D layer orientation as well as its correlated electrical conductivity and surface property. We unveil that 2D PtTe2 layers undergo three distinct growth mode transitions, i.e., horizontally aligned holey layers, continuous layer-by-layer lateral growth, and horizontal-to-vertical layer transition. This growth transition is a consequence of competing thermodynamic and kinetic factors dictated by accumulating internal strain, analogous to the transition of Frank-van der Merwe (FM) to Stranski-Krastanov (SK) growth in epitaxial thin-film models. The exclusive role of the strain on dictating 2D layer orientation has been quantitatively verified by the transmission electron microscopy (TEM) strain mapping analysis. These centimeter-scale 2D PtTe2 layers exhibit layer orientation tunable metallic transports yielding the highest value of ∼1.7 × 106 S/m at a certain critical thickness, supported by a combined verification of density functional theory (DFT) and electrical measurements. Moreover, they show intrinsically high hydrophobicity manifested by the water contact angle (WCA) value up to ∼117°, which is the highest among all reported 2D TMDCs of comparable dimensions and geometries. Accordingly, this study confirms the high material quality of these emerging large-area 2D PtTe2 layers, projecting vast opportunities employing their tunable layer morphology and semimetallic properties from investigations of novel quantum phenomena to applications in electrocatalysis.

Generation of a large compressive strain wave in graphite by ultrashort-pulse laser irradiation.

We have studied strain wave generation in graphite induced by an intense ultrashort laser pulse. The study was performed in the intensity regime above the ablation threshold of graphite. The aim was to maximize the strain and, thus, also the internal pressure (stress). Laser pulses with a 1 ps temporal duration melt the surface of graphite resulting in a molten material which initially exists at the solid density. As the molten material expands, a compressive strain wave starts propagating into the crystal below the molten layer. The strain pulse was studied with time-resolved X-ray diffraction. At a temporal delay of 100 ps after laser excitation, we observed >10% compressive strain, which corresponds to a pressure of 7.2 GPa. This strain could be reproduced by hydrodynamic simulations, which also provided a temperature map as a function of time and depth.

The haemodynamic effects of crystalloid and colloid volume resuscitation on primary, derived and efficiency variables in post-CABG patients.

BACKGROUND: Recent studies in haemodynamic management have focused on fluid management and assessed its effects in terms of increase in cardiac output based on fluid challenges or variations in pulse pressure caused by cyclical positive pressure ventilation. The theoretical scope may be characterised as Starling-oriented. This approach ignores the actual events of right-sided excitation and left-sided response which is consistently described in a Guyton-oriented model of the cardiovascular system. AIM: Based on data from a previous study, we aim to elucidate the primary response to crystalloid and colloid fluids in terms of cardiac output, mean blood pressure and right atrial pressure as well as derived and efficiency variables defined in terms of Guyton venous return physiology. METHOD: Re-analyses of previously published data. RESULTS: Cardiac output invariably increased on infusion of crystalloid and colloid solutions, whereas static and dynamic efficiency measures declined in spite of increasing pressure gradient for venous return. DISCUSSION: We argue that primary as well as derived and efficiency measures should be reported and discussed when haemodynamic studies are reported involving fluid administrations.

Clinicians' attitudes toward standardized assessment and diagnosis within child and adolescent psychiatry.

BACKGROUND: There is a strong call for clinically useful standardized assessment tools in everyday child and adolescent psychiatric practice. The attitudes of clinicians have been raised as a key-facilitating factor when implementing new methods. An explorative study was conducted aimed to investigate the clinicians' attitudes regarding standardized assessments and usefulness of diagnoses in treatment planning. METHODS: 411 mental health service personnel working with outpatient and inpatient assessment and treatment within the specialist child and adolescent mental health services, Stockholm County Council were asked to participate in the study, of which 345 (84%) agreed answer a questionnaire. The questionnaire included questions regarding Attitudes toward Standardized Assessment and Utility of Diagnosis. Descriptive analyses were performed and four subscales were compared with information from a similar study in US using the same instruments. The demographic and professional characteristics (age, working years, gender, education, profession, management position, involvement in assessment, level of service) in terms of prediction of attitudes were studied by univariate and multivariate linear regressions. RESULTS: Overall, the clinicians had quite positive attitudes and were more positive compared to a similar study conducted in the US earlier. There were differences in attitudes due to several characteristics but the only characteristic predicting all subscales was type of profession (counselor, nurse, psychiatrist, psychologist, other), with counselors being less positive than other groups. CONCLUSION: The overall positive attitudes toward standard assessment are of importance in the development of evidence-based practice and our study implies that clinicians in general value and are willing to use standardized assessment. Nevertheless, there are specific issues such as adequate training and available translated assessment instrument that need to be addressed. When implementing new methods in practice, there are general as well as specific resistances that need to be overcome. Studies in different cultural settings are of importance to further extend the knowledge of what is general and what is specific barriers.