Principles Study Research Articles

Selective Capture and Manipulation of DNA through Double Charged Nanopores.

In the past few decades, nanometer-scale pores have been employed as powerful tools for sensing biological molecules. Owing to its unique structure and properties, solid-state nanopores provide interesting opportunities for the development of DNA sequencing technology. Controlling DNA translocation in nanopores is an important means of improving the accuracy of sequencing. Here we present a proof of principle study of accelerating DNA captured across targeted graphene nanopores using surface charge density and find the intrinsic mechanism of the combination of electroosmotic flow induced by charges of nanopore and electrostatic attraction/repulsion between the nanopore and ssDNA. The theoretical study performed here provides a new means for controlling DNA transport dynamics and makes better and cheaper application of graphene in molecular sequencing.

Spatiotemporal organization of prefrontal norepinephrine influences neuronal activity.

Norepinephrine (NE), a neuromodulator released by locus coeruleus (LC) neurons throughout cortex, influences arousal and learning through extra-synaptic vesicle exocytosis. While NE within cortical regions has been viewed as a homogenous field, recent studies have demonstrated heterogeneous axonal dynamics and advances in GPCR-based fluorescent sensors permit direct observation of the local dynamics of NE at cellular scale. To investigate how the spatiotemporal dynamics of NE release in the prefrontal cortex (PFC) affect neuronal firing, we employed in vivo two-photon imaging of layer 2/3 of PFC in order to observe fine-scale neuronal calcium and NE dynamics concurrently. In this proof of principle study, we found that local and global NE fields can decouple from one another, providing a substrate for local NE spatiotemporal activity patterns. Optic flow analysis revealed putative release and reuptake events which can occur at the same location, albeit at different times, indicating the potential to create a heterogeneous NE field. Utilizing generalized linear models, we demonstrated that cellular Ca2+ fluctuations are influenced by both the local and global NE field. However, during periods of local/global NE field decoupling, the local field drives cell firing dynamics rather than the global field. These findings underscore the significance of localized, phasic NE fluctuations for structuring cell firing, which may provide local neuromodulatory control of cortical activity.Significance Statement NE is a neuromodulator which plays a critical role in learning and arousal, but understanding its spatial scale has been limited by technical barriers. Here, we utilized two-photon imaging of GPCR-based sensors, light sheet imaging, and computational modeling to gain insight into the fine scale organization of NE in PFC. We found that NE can influence neuronal activity at a local scale within cortex, which has not been shown before, and we developed new computational approaches to analyzing two-photon imaging of GPCR based fluorescent sensors. This insight will facilitate improved understanding of NE's role in motivated behaviors, as well as new approaches for understanding local neurotransmitter function.

Abstract PO4-19-01: The SURVIVE-HERoes trial – a secondary adjuvant treatment intervention study with trastuzumab-deruxtecan in patients with HER2 positive/HER2 low early breast cancer and a molecular relapse, based on a positive ctDNA result

Abstract Background: Despite current adjuvant treatment strategies, ≥ 20% of patients with early breast cancer (EBC) experience a metastatic relapse. In the new era of highly effective antibody drug conjugates (ADCs), secondary adjuvant treatment options for EBC patients at a high risk of relapse arise. The ADC trastuzumab-deruxtecan (T-DXd) has so far shown promising efficacy in patients with HER2-positive and HER2-low metastatic breast cancer (DESTINY Breast 03 and -04 trial) and is currently tested in the post-neoadjuvant setting in patients with non-pCR (DESTINY Breast 05 (TRUDY) trial). However, to successfully apply ADCs as a secondary adjuvant treatment, identification of patients who would benefit the most is required. The detection of minimal residual disease (MRD) using liquid biopsy, e.g. ctDNA, may offer a promising approach for patient selection. The efficacy of such a secondary adjuvant treatment in terms of delaying or even preventing distant metastases has yet to be evaluated in a randomized clinical trial. Trial design: The SURVIVE-HERoes trial is a prospective, randomized, open label comparative Phase III superiority trial in patients with intermediate to high-risk HER2-positive or HER2-low EBC, who participate in the large breast cancer surveillance trial SURVIVE (NCT05658172) and experience a molecular relapse as determined by a positive ctDNA result, but show no evidence of relapse or metastatic disease based on imaging by CT-scan and SPECT. In total, 180 patients will be enrolled and randomized with 2:1 allocation to treatment with T-DXd + (only endocrine therapy, if HR positive) versus standard of care (including endocrine treatment +/- CDK4/6-inhibitors or Neratinib). The treatment period lasts 12 months during which ctDNA levels will be repeatedly measured every 3 months (additional ctDNA testing will be performed at month 24 and 36). Stratification factors are HER2-, hormonal- and nodal status. Recruitment start is planned for Q1 2024. Eligibility criteria: Eligible patients are adult females/males, with HER2-positive or HER2-low EBC, as defined in the ASCO-CAP guidelines, and a positive ctDNA result (obtained in the SURVIVE study) that has to be confirmed ≤ 8 weeks before randomization. Primary anti-tumor therapy (surgery, adjuvant chemo- or radiotherapy) has to be completed ≥14 months, (postneo)-adjuvant treatment with anti-HER2-antibodies, T-DM1, Capecitabine, Pembrolizumab and Olaparib ≥ 4 weeks before randomization. Adequate bone marrow and cardiac function and no signs of ILD are mandatory. Statistics: The primary objective of SURVIVE-HERoes is the comparison of ctDNA clearance rates 6 months after randomization between the two study arms, which will be analysed using the chi square test for two independent proportions. Secondary objectives include the comparison of overall survival (OS), invasive disease-free survival (IDFS), distant disease-free survival (DDFS), distant recurrence-free survival (DRFS), breast cancer specific survival (BCSS), invasive breast cancer free survival (IBCFS) and quality of life (QoL) between the study arms as well as the safety and tolerability of T-DXd. Secondary survival endpoints will be estimated by the Kaplan Meier method and compared between the randomization arms using log-rank tests and cox regression models. Special aims: This trial is a proof of principle study with the aim to establish the efficacy of secondary adjuvant treatment with the ADC T-DXd in patients with HER2-positive/HER2-low early breast cancer, who are at high risk of relapse, as evidenced by detection of ctDNA in the blood. Conclusion: If SURVIVE-HERoes is successful, it could lead to a treatment shift towards early intervention with secondary adjuvant targeted therapies following liquid-biopsy based MRD detection. Contact: University Hospital Ulm, Dpt. Obstetrics & Gynecology, Germany, mail: studienzentrale.ufk@uniklinik-ulm.de Citation Format: Sophia Huesmann, Franziska Mergel, Kerstin Pfister, Angelina Fink, Forca Mehmeti, Peter Möller, Tanja Fehm, Volkmar Müller, Klaus Pantel, Thomas Friedl, Andreas Hartkopf, Brigitte Rack, Wolfgang Janni. The SURVIVE-HERoes trial – a secondary adjuvant treatment intervention study with trastuzumab-deruxtecan in patients with HER2 positive/HER2 low early breast cancer and a molecular relapse, based on a positive ctDNA result [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-19-01.

Unraveling the potential of transition metals as single atom catalyst in Graphene/WS2 van der Waals heterostructure for enhanced HER performance – A first principles study

Hydrogen, renowned for its abundance and versatility, stands as a significant green energy alternative, especially when produced through water electrolysis. In this study, 2D/2D van der Waals heterostructure with graphene and WS2 monolayer (GW) is constructed as electrocatalyst for hydrogen evolution reaction (HER). The cohesive energy and the binding energy per area for the GW heterostructure are found to be −0.39 eV and −18.9 meV/Å2 which confirms the structural stability as well as the weak binding of two monolayers. Furthermore, ten 3d transition metals are introduced as single atom catalyst (SAC) in the GW heterostructure (TM@GW) to enhance the catalytic performance. The ΔGH* for all TM@GW shows that there is an enrichment in the HER performance by 47–96 % upon the introduction of SAC, showcasing the superiority of Zn@GW heterostructure with an overpotential of 80 mV and the lowest kinetic barrier of 0.51 eV for the Volmer-Tafel reaction. This investigation provides valuable insight for modeling both van der Waals heterostructures and SACs to enrich catalytic performance.

First principles study of magneto-electronic and thermoelectric properties of quaternary CoZrMnSb for spintronics and waste heat recovery energy applications

First principles study of magneto-electronic and thermoelectric properties of quaternary CoZrMnSb for spintronics and waste heat recovery energy applications

Meshing principle and numerical study of classic conic worm drive

To explore the meshing mechanism of classic conic worm drive and provide a theoretical basis for creating other types of worm drive, a complete meshing theory on the proposed worm pair and its meshing performance are investigated. A new mathematical model containing a full set of geometric parameters on this drive is established using differential geometry. The formulae for calculating the reference point coordinates in different coordinate systems are attained, and then the blank size of the conical worm wheel is given. To build tooth surface boundaries, the meshing theory based on reference point is applied, which ensures the location of this point on the tooth surface. By solving multivariate nonlinear equation system in MATLAB environment, these conjugate regions and instantaneous contact lines are plotted within the axial section of the conic worm pair, at the same time, these values of sliding angle and induced principal curvature at meshing points are calculated. Finally, a numerical study is performed and the results verify that the conic worm pair has a relatively high tooth surface utilization ratio and favorable conditions for contact stress and lubrication, which is consistent with the practical application.

Estimating pedestrian walking speed at street crossings using the YOLOv4 and deep SORT algorithms: Proof of principle

There is evidence that existing standards for signal timing do not provide enough time for many pedestrians to safely cross intersections. Yet, current methods for studying this problem rely on inefficient manual observations. The objective of this work was to determine if the YOLOv4 and Deep SORT computer vision algorithms have the potential to be incorporated into automated measurement systems to measure and compare pedestrian walking speeds at one-stage and two-stage street crossings captured in birds-eye-view video. Walking speed was estimated for 1018 pedestrians at single-stage (591 pedestrians) and two-stage (427 pedestrians) street crossings. Pedestrians in the one-stage crossing were found to be significantly slower than pedestrians who crossed the two-stage crossing in one signal (1.19 ± 0.50 vs. 1.31 ± 0.49 m/s, p < 0.001). This proof of principle study demonstrated that the YOLOv4 and Deep SORT approaches are promising for estimating pedestrian walking speed.

Understanding the role of transition metal implantation on 2D graphitic carbon nitride for solid-state hydrogen storage: A first principles study

Modifying 2D materials with transition metals (TMs) proves to be an effective approach for enhancing their properties in hydrogen storage. In this article, the hydrogen interaction and adsorption over transition metal (TM) atoms (V, Mn, Fe, and Cu) implanted graphitic carbon nitride (gC3N4) is investigated using density functional theory (DFT). The stability of the TM atom on the gC3N4 surface is studied using binding energy and charge density calculations. The adsorption of H2 on the gC3N4 and TM-implanted gC3N4 surfaces is studied using adsorption energy, density of states (DOS), projected density of states (PDOS), charge density difference, and Lowdin occupancy analysis. The obtained results show that the Fe-gC3N4 system exhibits the highest adsorption energy of −1.025 eV for one H2. It is found that each Fe atom implanted on gC3N4 can stably adsorb up to 8H2 molecules, and the average adsorption energy of the 8H2 molecules is −0.201 eV/H2. In the context of practical applications for these materials, desorption is investigated employing the van't Hoff equation. Our findings affirm that the Fe-gC3N4 system can serve as an efficient material for solid-state hydrogen storage.

Adsorption of Zn atoms by monolayer WS2 doped with different atoms X (X = O, Se, N, P, F, Cl): first principles study.

The effect of X (X = O, Se, N, P, F, Cl) doping on the adsorption of Zn atoms by WS2 was investigated based on first principles. The electronic structure and optical properties of the adsorbed system after atomic doping were calculated. It is found that the Zn atom adsorbed on the W top (Tw) site has the most stable structure. When an S atom is replaced with an X atom based on the adsorption system, where the adsorption energy decreases after doping of O, P, F, and Cl atoms compared to the undoped system, it means that each system is more stable after doping of these atoms; charge transfer shows that the adsorption system after P-atom doping the system around the Zn atom loses electrons while S-atom gains electrons, which indicates that P-atom doping is favorable for the adsorption of Zn by WS2, N, P-atom is introduced as p-type doping and F, Cl-atom is introduced undoped by n-type doping, and the band gap of the doped system is less than that of the undoped one. With the introduction of different dopant atoms, certain impurity energy levels are introduced into the adsorption system. The prohibited bandwidth around the Fermi energy level reduces the density of states, causing the doped system's density of states to shift to lower energies, among which the shifts of N, P, F, and Cl are more pronounced. The P-doped adsorption system shows a new peak near the energy of - 11 eV. In addition, the study of optical properties showed that the peak reflections of both doped and non-doped systems adsorbing Zn atoms appeared in the ultraviolet region; the absorbance coefficient of the doped system is moved in the lower energy direction and red-shifted after atom doping; in addition, the absorption coefficients and reflectance of the P, Se doped systems are enhanced in the wavelength range of 200-300 nm compared with that before doping, the dielectric function and CBM and VBM positions were also calculated further indicating the potential of Se-doped systems in improving photocatalytic efficiency. In this paper, the structure optimization of X (X = O, Se, N, P, F, Cl) doping on WS2 adsorbed Zn atom model is performed based on the CASTEP module in Materials-Studio software under the first principles using GGA and PBE generalized function. The corresponding binding energies, bond lengths, bond angles, charge densities, energy band structures, densities of states, and optical properties were also analyzed. The Monkhorst-Pack particular K-point sampling method is used in the calculations; the K-point grid is 6 × 6 × 1, and the cutoff energy for the plane wave expansion is 500 eV. After geometric optimization, the iterative accuracy converges to a value of less than 1 × 10-5 eV/atom for the total energy of each atom and less than 0.03 eV/Å for all atomic forces. The thickness of the vacuum layer was set to 20 Å to avoid the effect of interlayer interaction forces. In this paper, 27 atoms were used to form a 3 × 3 × 1 supercellular tungsten disulfide system consisting of 18 S atoms and 9 W atoms.

First Principles Study of the Effects of Si, P, and S on the ∑5 (210)[001] Grain Boundary of γ-Fe

First Principles Study of the Effects of Si, P, and S on the ∑5 (210)[001] Grain Boundary of γ-Fe

Insight into Na and Sn substitutions on structural, electronic and thermodynamic responses of Li2FeSiO4 for next generation Li+-ion based batteries: A first principles study

In this study, Li2FeSiO4 has emerged as a promising alternative cathode material for next-generation Li-ion-based batteries due to its high theoretical capacity. We used spin density functional to investigate the structural, electronic, and thermodynamic responses of the pure and doped Li16Fe8Si8O32 system. In the Li-site is substituted by Li61Na3Fe32Si32O128, Li59Na5Fe32Si32O128, Li56Na8Fe32Si32O128, and in the Si-site, Li64Fe32Si31Sn1O128, Li64 Fe32Si30Sn2O128, Li64Sn4Fe32Si28O128 atoms, employing the Perdew-Burke-Ernzerhof (PBE) with generalized gradient approximation (GGA). The introduction of dopants induces significant modifications in the lattice parameters and corresponding volumes, thereby affecting the overall structural characteristics. The computed band gaps of both systems experience a decrease in the presence of dopants, indicating an enhancement in electronic conductive responses. The calculated results show that the band gap of Na-doped can be changed from 2.66 eV to 1.94 eV, and Sn-doped can be changed from 2.66 eV to 0.89 eV, respectively. The element, partial, and total density of states investigations reveal impurity states created by the modified atoms extending to the conduction band maximum. Intriguingly, Na and Sn concentrations in the pure system contribute to modified electronic conductivity attributed to volumetric expansion, a narrowed band gap, and reduced ionic bonding. In this analysis, we have recognized four new thermodynamically stable systems within the Li–Si–Fe–O system, both pure and dopant systems complementing each other. The computational investigations presented here are expected to contribute to a deeper understanding of the doping effects on Li2FeSiO4, facilitating further advancements in cathode material design for Li-ion batteries.

A first principle study of the heterogeneous catalysis mechanism of NaCl/KCl powder in suppressing combustion

Studies have shown that alkali metal ultrafine water mist additives, such as NaCl and KCl, are highly effective in inhibiting explosion and combustion. In order to further study the heterogeneous catalytic inhibition of NaCl and KCl, the 100 most stable surfaces of NaCl and KCl were selected as the research objects. Three typical free radicals (H, O, OH) were selected as surface adsorbents with different coverages, and the most stable adsorption sites and configurations were located. The NEB method was used to calculate the minimum energy paths of H and O recombination on two surfaces. The molecular dynamics of two surface combustion radicals were simulated by the AIMD method. The results indicated that NaCl and KCl have strong adsorption capacity for the O free radical, while the two surfaces have weaker adsorption capacity for the H free radical; NaCl and KCl, two catalytic active substances, which can eliminate H radicals through the continuous adsorption of H free radical to generate H2, and H radical is inactivated. The catalytic fire-extinguishing effect by eliminating O free radical is weak. Molecular dynamics calculations on the two surfaces revealed that Cl atoms precipitate differently under the adsorption of various radicals.

Comparative Investigation of Pressure Effect on Structural Stability, Electronic and Optical Response of LaXO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; (X = Al, In, Ga) for Optoelectronic Applications

A first principle study intense on the density functional theory with Heydscuseria-Ernzerhof screened hybrid functional hybrid function (HSEO6) is used to assess the structural, Electronic, elastic, mechanical and optical responses of LaXO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; (X = Al, In, Ga) perovskite materials. The compressive investigation under the external static isotropic pressure (P= 0 to 80GaP), phase stability, band structure and their important impact on the optical response of LaAlO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;, LaInO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; and LaGaO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;. Electronic band structure shows that LaXO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; (X = Al, In Ga) semiconductor with indirect band gap and an optically inactive response up to 20GPa, while the band gap becomes direct at 80GaP. There are gamma points (G-X-Q) at 80GPa and the band gap changes from indirect to direct nature. Under main desperation physical parameters of perovskite materials are well explained the response of TDOS, PDOS and EPDOS contour plots have been well understood for the full description of the band gap. It is further observed that the external pressure enhanced upto 40GPa both materials are significantly more mechanically stable compared to pristine LaXO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; (X = Al, In, Ga) at 0GPa. The optical properties of LaAlO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;, LaGaO&amp;lt;sub&amp;gt;3 &amp;lt;/sub&amp;gt;and LaInO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;, dielectric coefficient &amp;lt;i&amp;gt;(ε&amp;lt;sub&amp;gt;1&amp;lt;/sub&amp;gt;, iε&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;)&amp;lt;/i&amp;gt; have been employed along with the optical responses like absorption, energy loss function, reflectivity and reflective index are obtained in the energy scale from 0 to 60 eV. It was observed that static dielectric constant decreases with the decrease in optical band gap. The optical tunings under the effect of pressure which are good candidates in practical optoelectronic applications are extensively used and interpreted by the calculation of the dielectric function.

First Principles Study of the Structure-Performance Relation of Pristine Wn+1Cn and Oxygen-Functionalized Wn+1CnO2 MXenes as Cathode Catalysts for Li-O2 Batteries.

Li-O2 batteries are considered a highly promising energy storage solution. However, their practical implementation is hindered by the sluggish kinetics of the oxygen reduction (ORR) and oxygen evolution (OER) reactions at cathodes during discharging and charging, respectively. In this work, we investigated the catalytic performance of Wn+1Cn and Wn+1CnO2 MXenes (n = 1, 2, and 3) as cathodes for Li-O2 batteries using first principles calculations. Both Wn+1Cn and Wn+1CnO2 MXenes show high conductivity, and their conductivity is further enhanced with increasing atomic layers, as reflected by the elevated density of states at the Fermi level. The oxygen functionalization can change the electronic properties of WC MXenes from the electrophilic W surface of Wn+1Cn to the nucleophilic O surface of Wn+1CnO2, which is beneficial for the activation of the Li-O bond, and thus promotes the Li+ deintercalation during the charge-discharge process. On both Wn+1Cn and Wn+1CnO2, the rate-determining step (RDS) of ORR is the formation of the (Li2O)2* product, while the RDS of OER is the LiO2* decomposition. The overpotentials of ORR and OER are positively linearly correlated with the adsorption energy of the RDS LixO2* intermediates. By lowering the energy band center, the oxygen functionalization and increasing atomic layers can effectively reduce the adsorption strength of the LixO2* intermediates, thereby reducing the ORR and OER overpotentials. The W4C3O2 MXene shows immense potential as a cathode catalyst for Li-O2 batteries due to its outstanding conductivity and super-low ORR, OER, and total overpotentials (0.25, 0.38, and 0.63 V).

In Situ Imaging of Subcutaneous Drug Delivery Systems Using Microspatially Offset Low-Frequency Raman Spectroscopy.

The noninvasive in situ monitoring of the status of drug retention and implant integrity of subcutaneous implants would allow optimization of therapy and avoid periods of subtherapeutic delivery kinetics. A proof-of principle study was conducted to determine the use of microspatially offset low-frequency Raman spectroscopy (micro-SOLFRS) for nonintrusive in situ analysis of subcutaneous drug delivery systems. Caffeine was used as the model drug, and it was embedded in a circular-shape Soluplus matrix via vacuum compression molding. For the exploratory analysis, prototype implants were positioned underneath skin tissue samples, and various caffeine concentrations (1-50% w/w) and micro-SOLFRS displacement settings (Δz = 0-8 mm) were tested from the pseudo three-dimensional (3D)-imaging perspective. This format allowed the optimization of real-time micro-SOLFRS analysis of implants through skin tissue that was embedded in an agarose hydrogel. Notably, this analytical approach allowed the temporal and spatial erosion of the implant and solid-state transformations of caffeine to be distinguished. The spectrometric results correlated with complementary high-performance liquid chromatography (HPLC) determination of changes in drug concentration, illustrating drug dissipation/diffusion characteristics. The discovered capability of micro-SOLFRS for in situ measurements of drugs and implants makes it attractive for biomedical diagnostics that, ultimately, could result in development of a new point-of-care technology.

First principles study on heterogeneous interfaces of TiCu alloys through aluminum addition

This paper investigates the heterogeneous nucleation interface resulting from the addition of Al element to TiCu alloy, focusing on the essential phases Ti2Cu and TiCu. Employing first principles calculations, we explore the refinement mechanism of this interface. Initially, the lattice mismatch between Al/Ti2Cu and Al/TiCu interfaces is calculated to assess the potential for heterogeneous nucleation. Four distinct interfacial types are established following a surface convergence test. The adhesive work (Wad) and Interfacial energy (γ) are computed for each interface to ascertain their crystallization potential. Furthermore, the differential charge density (DCD) and projected density of states (PDOS) for the four interfacial types are determined to analyze bonding characteristics. Results indicate a mismatch degree of 4.09 % for Al (110)/Ti2Cu (110) and 5.29 % for Al (110)/TiCu (110). These values suggest a tendency to form a heterogeneous interface with a coherent lattice, primarily characterized by Cu-Al and Ti-Al metallic bonds. The Al-Ti2Cu interface exhibits a larger nucleation work of 2.23 J/m2 and a smaller interface energy of −53.007 J/m2. This study demonstrates that Al effectively serves as a heterogeneous nucleation center within the Ti2Cu/TiCu system, contributing to substrate phase refinement and strengthening the TiCu alloy. The optimization of these findings provides valuable insights into the alloy's microstructural evolution, facilitating the design and enhancement of advanced materials for diverse applications.

Structural and optoelectronic properties of 2D halide perovskites Cs2MBr4 (M = Zn, Cd, Hg): a first principle study

Structural and optoelectronic properties of 2D halide perovskites Cs2MBr4 (M = Zn, Cd, Hg): a first principle study

First principles study of electronic structure and transport in graphene grain boundaries

Grain boundaries play a major role for electron transport in graphene sheets grown by chemical vapor deposition. Here we investigate the electronic structure and transport properties of idealized graphene grain boundaries (GBs) in bi-crystals using first principles density functional theory (DFT) and non-equilibrium Greens functions. We generated 150 different grain boundaries using an automated workflow where their geometry is relaxed with DFT. We find that the GBs generally show a quasi-1D bandstructure along the GB. We group the GBs in four classes based on their conductive properties: transparent, opaque, insulating, and spin-polarizing and show how this is related to angular mismatch, quantum mechanical interference, and out-of-plane buckling. Especially, we find that spin-polarization in the GB correlates with out-of-plane buckling. We further investigate the characteristics of these classes in simulated scanning tunnelling spectroscopy and diffusive transport along the GB which demonstrate how current can be guided along the GB.

Thermodynamic properties of rhodium—A first principle study

The high-pressure and high-temperature thermodynamic properties of rhodium (up to 2000 K and 300 GPa) are presented using the first principle approach within the quasi-harmonic approximation. The thermal Helmholtz free energy includes the contribution of both phonon vibrations and electronic excitations. The performance of three popular exchange-correlation functionals—local density approximation [Perdew et al., Phys. Rev. B 23, 5048 (1981)], Perdew–Burke–Ernzerhof generalized gradient approximation (PBE) [Perdew et al., Phys. Rev. Lett. 77, 3865 (1996)], PBE modified for dense solids [Perdew et al., Phys. Rev. Lett. 100, 136406 (2008)] are shown. The simulated thermal expansion coefficient, isobaric heat capacity, mode-Grüneisen parameter, thermodynamic average Grüneisen parameter, and bulk modulus are compared with the available experimental and theoretical reports. The contribution of thermal electronic excitations to the obtained thermodynamic parameters is significant at low pressure and high temperatures, except in bulk modulus, where it is small. The pressure-dependent elastic constant coefficient (Cij) and the Debye temperature are computed at 0 K. The Pugh ratio calculated from Cij indicates that rhodium undergoes brittle to ductile transitions at an average pressure of 7.45 GPa.

First principles study on the time-related properties of 4H-32SiC as an energy converting material of betavoltaic batteries

The radioactive 4H-32SiC is applied as an energy converting material to fabricate high performance betavoltaic batteries. The time-related component change is considered, and the structural, stability and electrical property changes are calculated by density functional theory. As time goes by, the number of 32Si atoms decrease exponentially while the concentration of 32S increases gradually. The Si63PC64 configurations have smaller lattice constants, while the lattices of Si62PSC64 configurations are larger. All Si63PC64 and Si62PSC64 configurations have very small bandgaps indicating the metallic behavior. This suggests that the betavoltaic battery with 4H-32SiC is likely to transform into a Schottky diode over time.