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1.	Atthapak, Chayanon, et al. (författare) Thermodynamic Stability Prediction of Triple Transition-Metal (Ti-Mo-V)3C2 MXenes via Cluster Correlation-Based Machine Learning 2024 Ingår i: Advanced Theory and Simulations. - : WILEY-V C H VERLAG GMBH. - 2513-0390. Tidskriftsartikel (refereegranskat)abstract The representation of atomic configurations through cluster correlations, along with the cluster expansion approach, has long been used to predict formation energies and determine the thermodynamic stability of alloys. In this work, a comparison is conducted between the traditional cluster expansion method based on density functional theory and other potential machine learning models, including decision tree-based ensembles and multi-layer perceptron regression, to explore the alloying behavior of different elements in multi-component alloys. Specifically, these models are applied to investigate the thermodynamic stability of triple transition-metal ((Ti-Mo-V)(3)C-2 MXenes, a multi-component alloy in the largest family of 2D materials that are gaining attention for several outstanding properties. The findings reveal the triple transition-metal ground-state configurations in this system and demonstrate how the configuration of transition metal atoms (Ti, Mo, and V atoms) influences the formation energy of this alloy. Moreover, the performance of machine learning algorithms in predicting formation energies and identifying ground-state structures is thoroughly discussed from various aspects.
2.	Brinck, Tore, 1965-, et al. (författare) The Molecular Surface Property Approach : A Guide to Chemical Interactions in Chemistry, Medicine, and Material Science 2019 Ingår i: Advanced Theory and Simulations. - : WILEY-V C H VERLAG GMBH. - 2513-0390. ; 2:1 Tidskriftsartikel (refereegranskat)abstract The current status of the molecular surface property approach (MSPA) and its application for analysis and prediction of intermolecular interactions, including chemical reactivity, are reviewed. The MSPA allows for identification and characterization of all potential interaction sites of a molecule or nanoparticle by the computation of one or more molecular properties on an electronic isodensity surface. A wide range of interactions can be analyzed by three properties, which are well-defined within Kohn-Sham density functional theory. These are the electrostatic potential, the average local ionization energy, and the local electron attachment energy. The latter two do not only reflect the electrostatic contribution to a chemical interaction, but also the contributions from polarization and charge transfer. It is demonstrated that the MSPA has a high predictive capacity for non-covalent interactions, for example, hydrogen and halogen bonding, as well as organic substitution and addition reactions. The latter results open u p applications within drug design and medicinal chemistry. The application of MSPA has recently been extended to nanoparticles and extended surfaces of metals and metal oxides. In particular, nanostructural effects on the catalytic properties of noble metals are rationalized. The potential for using MSPA in rational design of heterogeneous catalysts is discussed.
3.	Brorsson, Joakim, 1988, et al. (författare) Efficient Calculation of the Lattice Thermal Conductivity by Atomistic Simulations with Ab Initio Accuracy 2022 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 5:2 Tidskriftsartikel (refereegranskat)abstract High-order force constant expansions can provide accurate representations of the potential energy surface relevant to vibrational motion. They can be efficiently parametrized using quantum mechanical calculations and subsequently sampled at a fraction of the cost of the underlying reference calculations. Here, force constant expansions are combined via the hiphive package with GPU-accelerated molecular dynamics simulations via the GPUMD package to obtain an accurate, transferable, and efficient approach for sampling the dynamical properties of materials. The performance of this methodology is demonstrated by applying it both to materials with very low thermal conductivity (Ba8Ga16Ge30, SnSe) and a material with a relatively high lattice thermal conductivity (monolayer-MoS2). These cases cover both situations with weak (monolayer-MoS2, SnSe) and strong (Ba8Ga16Ge30) pho renormalization. The simulations also enable to access complementary information such as the spectral thermal conductivity, which allows to discriminate the contribution by different phonon modes while accounting for scattering to all orders. The software packages described here are made available to the scientific community as free and open-source software in order to encourage the more widespread use of these techniques as well as their evolution through continuous and collaborative development.
4.	Cheng, Cheng, et al. (författare) Identification of High-Performance Single-Atom MXenes Catalysts for Low-Temperature CO Oxidation 2019 Ingår i: Advanced Theory and Simulations. - : WILEY-V C H VERLAG GMBH. - 2513-0390. ; 2:8 Tidskriftsartikel (refereegranskat)abstract On the basis of first-principles calculations, Fe, Co, Ni, Cu, Zn, Ru, Rh, Ag, Ir, Pt, and Au decorated Mo2CO2-delta monolayers are investigated as potential single-atom catalyst (SAC) candidates for low-temperature CO oxidation reaction. From a first screening based on intuitive criteria concerning metal sintering, CO poisoning, and O-2 adsorption strength, the Zn/Mo2CO2-delta system is selected for further scrutiny by means of reactivity calculations for different CO concentrations. A lower barrier is found for Eley-Rideal reaction mechanism than for the Langmuir-Hinshelwood mechanism. The low Eley-Rideal barrier (0.15 eV) is attributed to the fact that the Zn atom weakens the O-O bond considerably and the electrophilic attack of CO weakens it further. The main conclusion is that this system is a promising low-temperature SAC candidate with a lower energy barrier for CO oxidation than noble metal and other 2D SAC systems investigated.
5.	Ekspong, Joakim, et al. (författare) Theoretical Analysis of Surface Active Sites in Defective 2H and 1T ' MoS2 Polymorphs for Hydrogen Evolution Reaction : Quantifying the Total Activity of Point Defects 2020 Ingår i: Advanced Theory and Simulations. - : Wiley-VCH Verlagsgesellschaft. - 2513-0390. ; 3:3 Tidskriftsartikel (refereegranskat)abstract Defect engineering is a common and promising strategy to improve the catalytic activity of layered structures such as MoS2, where in particular the 2H and 1T ' polymorphs have been under intense study for their activity toward the hydrogen evolution reaction. However, the large variety of defects, each with its own distinct and usually unknown effects, complicates the design and optimization of such defective materials. Therefore, it is relevant to characterize in detail the effect of individual defects and to be able to combine these observations to describe more complex materials, such as those seen experimentally. Therefore, nine point defects (antisites defects and vacancies) are theoretically studied on single layer 1T, 1T ', and 2H MoS2 polymorphs, and the variation and spatial distribution in the active sites are identified. It is found that all defective 1T ' monolayers exhibit an increase in the exchange current density of at least 2.3 times when compared to pristine 1T ' MoS2, even if a reduced number of active sites are observed. The results are later used to propose a methodology to study materials containing a mixture of crystal phases, or other alterations that cause inhomogeneous changes in the activity of catalytic sites.
6.	Ektarawong, Annop, et al. (författare) Role of Al Vacancies in Thermodynamic Stability and Elastic Properties of AlB2-type (Ta,Al)B2: A First-Principles Study 2024 Ingår i: Advanced Theory and Simulations. - : WILEY-V C H VERLAG GMBH. - 2513-0390. Tidskriftsartikel (refereegranskat)abstract AlB2-type TaB2 is one of the transition-metal diborides, a class of refractory ceramics, that has increasingly received attention due particularly to their potential for hard-coating applications. In this work, the first-principles calculations are performed, in combination with the cluster-expansion method, to investigate the effect of mixing AlB2 with TaB2 on the thermodynamic stability, structural parameters, electronic density of states, and mechanical behavior of the resulting (Ta,Al)B-2 solid solutions. It is found that the solid solutions display the chemical ordering of Ta and Al atoms both residing on the metal sublattice of the material, together with the preference for partial substitution of vacancies for Al atoms. This results in the formation of Al-deficient (Ta,Al)B-2 with the chemical composition Ta0.6Al0.3B2, predicted to be thermodynamically stable even at absolute zero in the ternary Ta-Al-B system. It is further found that such formation of Al vacancies in (Ta,Al)B-2 not only enhances the stability of the solutions but also improves their elastic properties and hardness, both of which could be attributed to the effect of electronic band filling. This investigation indeed sheds light on the interplay between the mixing of Ta and Al atoms and the presence of Al vacancies on the alloying and mechanical behaviors of (Ta,Al)B-2, and it thus offers valuable insights for further research and development of these ceramics.
7.	Eriksson, Fredrik, 1992, et al. (författare) The Hiphive Package for the Extraction of High-Order Force Constants by Machine Learning 2019 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 2:5 Tidskriftsartikel (refereegranskat)abstract The efficient extraction of force constants (FCs) is crucial for the analysis of many thermodynamic materials properties. Approaches based on the systematic enumeration of finite differences scale poorly with system size and can rarely extend beyond third order when input data is obtained from first-principles calculations. Methods based on parameter fitting in the spirit of interatomic potentials, on the other hand, can extract FC parameters from semi-random configurations of high information density and advanced regularized regression methods can recover physical solutions from a limited amount of data. Here, the HIPHIVE Python package, that enables the construction of force constant models up to arbitrary order is presented. HIPHIVE exploits crystal symmetries to reduce the number of free parameters and then employs advanced machine learning algorithms to extract the force constants. Depending on the problem at hand, both over and underdetermined systems are handled efficiently. The FCs can be subsequently analyzed directly and or be used to carry out, for example, molecular dynamics simulations. The utility of this approach is demonstrated via several examples including ideal and defective monolayers of MoS2 as well as bulk nickel.
8.	Forro, Csaba, et al. (författare) Visualizing and Analyzing 3D Metal Nanowire Networks for Stretchable Electronics 2020 Ingår i: Advanced Theory and Simulations. - : John Wiley & Sons. - 2513-0390. ; 3:8 Tidskriftsartikel (refereegranskat)abstract Composites based on conductive nanowires embedded in elastomers are popular in a wide range of stretchable electronics applications where the requirements are either a stable or a highly increasing electrical resistance upon strain. Despite the widespread use of such composites, their production is not based in solid theoretical grounds but rather in empirical observations. The lack of such a framework is due to limitations in the methods for studying nanowire meshes, in particular the lack of knowledge on the spatial distribution of the nanowires and the change of their position under strain. This hurdle is overcome by collecting 3D reconstructed X-ray tomographies of silver nanowires embedded in polydimethylsiloxane (PDMS) under variable deformations and the missing structural information of the nanomaterial is obtained by unsupervised artificial intelligence image analysis. This allowed to reveal the precise assembly mechanisms of nanowire systems and derive a precise analytical formula for the piezoresistive response of the composite and finally to simulate the behavior of arbitrary samples in-silico.
9.	Fransson, Erik, 1990, et al. (författare) Dynasor - A Tool for Extracting Dynamical Structure Factors and Current Correlation Functions from Molecular Dynamics Simulations 2021 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 4:2 Tidskriftsartikel (refereegranskat)abstract Perturbative treatments of the lattice dynamics are widely successful for many crystalline materials; however, their applicability is limited for strongly anharmonic systems, metastable crystal structures and liquids. The full dynamics of these systems can, however, be accessed via molecular dynamics (MD) simulations using correlation functions, which includes dynamical structure factors providing a direct bridge to experiment. To simplify the analysis of correlation functions, here the dynasor package is presented as a flexible and efficient tool that enables the calculation of static and dynamical structure factors, current correlation functions as well as their partial counterparts from MD trajectories. The dynasor code can handle input from several major open source MD packages and thanks to its C/Python structure can be readily extended to support additional codes. The utility of dynasor is demonstrated via examples for both solid and liquid single and multi-component systems. In particular, the possibility to extract the full temperature dependence of phonon frequencies and lifetimes is emphasized.
10.	Friedman, Ran (författare) Simulations of Biomolecules in Electrolyte Solutions 2019 Ingår i: Advanced Theory and Simulations. - : Wiley-Blackwell. - 2513-0390. ; 2:4, s. 1-10 Tidskriftsartikel (refereegranskat)abstract Biomolecules including proteins, lipid membranes, and nucleic acids operate at an aqueous milieu that includes solvated ions. The interactions with ions affect biomolecules in different ways depending on the nature of the solute and the type of the ions. The dynamic nature of small soluble ions makes it difficult to follow them by structural methods. Consequently, theories were developed to explain how biomolecules interact in an environment that includes electrolytes. Moreover, simulations studies are often used to study such systems at the molecular or atomistic level. The status of the field, and inparticular of simulation studies, is the subject of this progress report.
11.	Khossossi, Nabil, et al. (författare) Exploring the Possibility of beta-Phase Arsenic-Phosphorus Polymorph Monolayer as Anode Materials for Sodium-Ion Batteries 2020 Ingår i: Advanced Theory and Simulations. - : Wiley-VCH Verlag. - 2513-0390. ; 3:8 Tidskriftsartikel (refereegranskat)abstract Graphite anode have shown commercial success for over two decades, since the start of their use in commercial Li-ion batteries, due to their high practical specific capacity, conductivity, and low lithiation potential. Graphite is to a large extent thermodynamically unfavorable for sodium-ion intercalation and thus limits advancement in Na-ion batteries. In this work, a beta-phase arsenic-phosphorus monolayer is studied, which has recently been predicted to have semiconducting behavior and to be dynamically stable. First-principles calculations based on density functional theory are used to explore the role of beta-AsP monolayer as a negative electrode for Na-ion batteries. Cohesive energy, phonon spectrum, and molecule dynamics simulations confirm the thermodynamic stability and the possibility of experimentally synthesizing this material. The Na-ion adsorption-energies are found to be high (>-1.2 eV) on both sides (As- and P-side). The ultra-fast energy barriers for Na (0.046/0.053 V) over both sides imply high diffusion of Na-ions on the surfaces of beta-AsP. During the evaluation of Na-ion anode performance, the fully sodiated state is found to be Na2AsP, which yields a high theoretical-specific capacity of 506.16 mAh g(-1)and low average sodiation potential of 0.43 V versus Na/Na+.
12.	Korolkovas, Airidas (författare) 5D Entanglement in Star Polymer Dynamics 2018 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 1:11 Tidskriftsartikel (refereegranskat)abstract Star polymers are within the most topologically entangled macromolecules. For a star to move the current theory is that one arm must retract to the branch point. The probability of this event falls exponentially with molecular weight, and a quicker relaxation pathway eventually takes over. With a simulation over a hundred times faster than earlier studies, it is demonstrated that the mean square displacement scales with a power law 1/16 in time, instead of the previously assumed zero. It suggests that star polymer motion is the result of two linear relaxations coinciding in time. By analogy to linear polymers, which reptate with a random walk embedded in a 3D network, we show that star polymers relax by a random walk in a 5D network.
13.	Lattemann, Martina, et al. (författare) Understanding Quality Control of Hard Metals in Industry - A Quantum Mechanics Approach 2019 Ingår i: Advanced Theory and Simulations. - : Wiley-VCH Verlagsgesellschaft. - 2513-0390. ; 2:6 Tidskriftsartikel (refereegranskat)abstract For many decades, the magnetic saturation of, for example, hard metals (HM) such as WC-Co-based cemented carbides, has been used as process and quality control in industry to ensure consistency of product properties. In an urge to replace cobalt as a binder phase, a demand on understanding the magnetic response as a function of composition on the atomic scale is growing. In this paper, a theoretical description of the measured weight-specific magnetic saturation of hard metals as a function of the tungsten weight fraction present in the cobalt binder phase, based on first-principle calculations, is established for standard WC-Co. The predicted magnetic saturation agrees well with the experimental one. Furthermore, it is proposed that the theoretical description can be extended to alternative and more complex binder phases which allows to transfer the production control to those hard metals.
14.	Liu, Yichao, et al. (författare) Fast Adaptive Thermal Buffering by a Passive Open Shell Based on Transformation Thermodynamics 2018 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 1:7 Tidskriftsartikel (refereegranskat)abstract By using transformation thermodynamics, an open, adaptive thermal buffer shell (TBS) is designed and experimentally implemented with natural materials (layered copper and expanded polystyrene [EPS]). The TBS can store excessive heat flux quickly in the shell and release it slowly when it is needed, which also has some distinctive features: first it is a buffer shell that can avoid external extremes in temperature (either high or low) and also provide a relatively stable temperature for the interior of the shell when the temperature outside the shell has some fluctuations; second the TBS is not thermally insulated (with holes connected to the outside world) and the buffering effect of the TBS originates from the heat recycling mechanics, not thermal insulation; third the TBS has a short response time and the temperature inside the shell can be quickly adjusted according to the average temperature outside the shell; fourth the TBS is a passive device. Unlike traditional air conditioning, the TBS can work without an external power supply. The TBS will have many applications in energy recycling systems, smart heat controlling systems, and passive heat self-adaptation systems. Numerical simulations and experimental demonstrations are given to verify the function of the TBS.
15.	Majdi, Saman, 1977-, et al. (författare) Carrier Scattering Mechanisms : Identification via the Scaling Properties of the Boltzmann Transport Equation 2021 Ingår i: Advanced Theory and Simulations. - : John Wiley & Sons. - 2513-0390. ; 4:1 Tidskriftsartikel (refereegranskat)abstract A method based on the scaling properties of the Boltzmann transport equation is proposed to identify the dominant scattering mechanisms that affect charge transport in a semiconductor. This method uses drift velocity data of mobile charges at different lattice temperatures and applied electric fields and takes into account the effect of carrier heating. By performing time‐of‐flight measurements on single‐crystalline diamond, hole and electron drift velocities are measured under low‐injection conditions within the temperature range 10–300 K. Evaluation of the data using the proposed method identifies acoustic phonon scattering as the dominant scattering mechanism across the measured temperature range. The exception is electrons at 100–200 K where conduction‐band valley repopulation has a prominent effect. At temperatures below ≈80 K, where valley polarization is observed for electrons, transport dominated by acoustic phonon scattering is observed in different valleys separately. The scaling model is additionally tested on data from highly resistive gallium arsenide samples to demonstrate the versatility of the method. In this case, impurity scattering can be ruled out as the dominant scattering mechanism in the samples for the temperature range 80–120 K.
16.	Manzetti, Sergio, et al. (författare) Analytical Solutions for a Supersymmetric Wave‐Equation for Quasiparticles in a Quantum System 2020 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 3:1 Tidskriftsartikel (refereegranskat)abstract Vortices and quasiparticles have been studied for 2D systems over the past decades in relation to the development of technologies in quantum electromagnetics, optics, and quantum computation. Deriving new equations for quasiparticles in quantum systems is therefore a critical part of quantum physics. Recently, a supersymmetric wave equation has been developed which describes quasiparticles and vorticity under the influence of electromagnetic fields which has been studied numerically. The analytical solutions of the supersymmetric wave‐equation are presented by increasing levels of energy. It is shown that the derived linear and nonlinear models of the supersymmetric wave‐equation can represent respectively symmetric and asymmetric vorticity formed in a confined rotating torus. The models described are suitable to represent vorticity formed in 2D and 3D electron gas and can be of significant relevance to future research in quantum electromagnetics.
17.	Manzetti, Sergio, et al. (författare) Electromagnetic Vorticity in a Square-Well Crystal System Described by a Supersymmetric Wave-Equation 2020 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 3:1, s. 1900186- Tidskriftsartikel (refereegranskat)abstract Vortices occur under all electromagnetic phenomena in quantized systems, as well as macroscopic systems. In particular, vorticity in square-wells is of great appeal to the scientific community, as it models electromagnetic fields and formation of condensates in crystal lattices. A supersymmetric wave-equation (SWE) is devised to model vorticity in a square-well system, and the numerical results of several states of vorticity are shown by increased energy of the system. It is shown that square-well vorticity obeys specific symmetries when modeled with the SWE and generates non-overlapping vortices of the same spin. Nucleation of vortices when subjected to increased angular velocity and formation of giant vortices is also shown. This is of importance to the modeling of magnetism in quantum systems, and the generation of new results to describe quantum vorticity.
18.	Manzetti, Sergio, et al. (författare) Supersymmetric Hamiltonian and Vortex Formation Model in a Quantum Nonlinear System in an Inhomogeneous Electromagnetic Field 2019 Ingår i: Advanced Theory and Simulations. - : John Wiley & Sons. - 2513-0390. ; 2:5 Tidskriftsartikel (refereegranskat)abstract Vortices and quasiparticles in 2D systems are studied for the last decades in relation to the development of technologies in quantum electromagnetics, optics, and quantum computation. Hamiltonians are a fundamental part for studying quasiparticles and vortices, and provide models to calculate the eigenvalues and eigenfunctions that describe a real physical state. By devising supersymmetry, a Hamiltonian for the description of vortices is developed forming in an 2D electron gas and study the numerical solutions under the effects of an alternating electromagnetic field. The numerical analysis shows that vorticity is formed spontaneously without symmetry‐breaking and vortices arise from the boundaries and converge toward the center of the system in a similar fashion to natural hydrodynamic phenomena in water or plasma. Additionally, the equation under damping conditions is studied, a homogenous magnetic field and under the absence of an electromagnetic field. The results and the study of the parameters indicate that the supersymmetic wave equation (SWE) may be a good model equation to describe vorticity for quantum electromagnetics, hydrodynamics, and other physical phenomena in the realm of physical and quantum physical sciences.
19.	Nikoulis, G., et al. (författare) NanoMaterialsCAD : Flexible Software for the Design of Nanostructures 2021 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 4:1 Tidskriftsartikel (refereegranskat)abstract NanoMaterialsCAD is a new open source tool dedicated to the creation, manipulation, and 3D visualization of crystalline structures at the nanoscale. It is designed for preprocessing atomistic configurations to be used as input for atomistic (e.g., molecular dynamics or Monte Carlo) or ab initio (e.g., density functional theory) computer simulations. It offers several tools for designing complex nanostructures (including nanoparticles, nanowires, nanotubes, nanoscrolls, etc., and combinations/permutations of them) which are either lacking or cumbersome in other existing packages. Through its intuitive graphical user interface (GUI) it enables facile ways to design and modify the size/shape and relative positions of nanoobjects while observing the changes in real time. NanoMaterialsCAD is written in C++, and exploits Open Graphics Library (OpenGL) (for the GUI), Win32API (for interaction with Windows), and Assembly (for fast data management). The source code and executable file are available for download from GitHub (https://github.com/cossphy/NanoMaterialsCAD). It is aspired that NanoMaterialsCAD will be adopted by the nanomaterials modeling community as a valuable resource; to this end it will be kept improving, incorporating more nanostructures, and adding extra functionalities to its toolbox.
20.	Panigrahi, Puspamitra, et al. (författare) Efficient Sensing of Selected Amino Acids as Biomarker by Green Phosphorene Monolayers : Smart Diagnosis of Viruses 2022 Ingår i: Advanced Theory and Simulations. - : John Wiley & Sons. - 2513-0390. ; 5:10 Tidskriftsartikel (refereegranskat)abstract Effective techniques for the detection of selected viruses detection of their amino acids (AAs) constituents are highly desired, especially in the present COVID pandemic. Motivated by this, we have used density functional theory (DFT) simulations to explore the potential applications of green phosphorene monolayer (GPM) as efficient nanobio-sensor. We have employed van der Waals induced calculations to study the ground-state geometries, binding strength, electronic structures, and charge transfer mechanism of pristine, vacancy-induced and metal-doped GPM to detect the selected AAs, such as glycine, proline and aspartic, in both aqueous and non-aqueous media. We find that the interactions of studied AAs are comparatively weak on pristine (-0.49 to -0.76 eV) and vacancy-induced GPM as compared to the metal-doped GPM (-0.62 to -1.22 eV). Among the considered dopants, Ag-doping enhances the binding of AAs to the GPM stronger than the others. In addition to appropriate binding energies, significant charge transfers coupled with measurable changes in the electronic properties further authenticate the potential of GPM. Boltzmann thermodynamic analysis have been used to study the sensing mechanism under varied conditions of temperatures and pressure for the practical applications. Our findings signify the potential of G PM based sensors towards efficient detection of the selected AAs.
21.	Popescu, Adrian, et al. (författare) Optical Response of MoTe2 and WTe2 Weyl Semimetals : Distinguishing between Bulk and Surface Contributions 2020 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 3:3 Tidskriftsartikel (refereegranskat)abstract A first-principles investigation of the optical response of the Weyl Semimetals MoTe2 and WTe2 is presented. The approach, based on combining two formulations, allows to both separate the intraband and interband parts of the optical conductivity and to distinguish between the bulk and surface contributions to the optical response. It is found that the response is truly anisotropic, with peaks that can be associated with interband transitions involving either bulk or surface states. The role of the relaxation time, and the relation of the calculated results with available experimental measurements, are also discussed. Furthermore, the approach reported is transferable to any system, topologically trivial or non-trivial, thus addressing the long-standing need for comprehensive characterization of the optical response.
22.	Rittiruam, Meena, et al. (författare) First-Principles Active-Site Model Design for High-Entropy-Alloy Catalyst Screening: The Impact of Host Element Selection on Catalytic Properties 2023 Ingår i: Advanced Theory and Simulations. - : WILEY-V C H VERLAG GMBH. - 2513-0390. Tidskriftsartikel (refereegranskat)abstract Active-site models comprise miniature active sites on the host element, providing one of effective descriptors for screening high-entropy-alloy (HEA) catalysts using machine learning. This study investigates the impact of host elements on the electronic properties of active sites via density functional theory (DFT), where the active-site model is used in the HEA electrocatalysts. Also, the appropriate host element selection significantly affects the systems surface structures, electronic, and catalytic properties that adsorbate adsorption energy, d-band center, Bader charge, Zero-point energy, and entropy are used as accuracy verification parameters compared to the original surface. Ultimately, the novel guideline for active-site model construction is proposed using the simple example of PtPdFeCoNi high-entropy alloys. This investigation demonstrates that the host element selection is a crucial parameter to the active-site models, influencing the electronic structure and electrocatalytic properties.
23.	Rittiruam, Meena, et al. (författare) First-Principles Density Functional Theory and Machine Learning Technique for the Prediction of Water Adsorption Site on PtPd-Based High-Entropy-Alloy Catalysts 2023 Ingår i: Advanced Theory and Simulations. - : WILEY-V C H VERLAG GMBH. - 2513-0390. ; 6:4 Tidskriftsartikel (refereegranskat)abstract The water-gas shift reaction (WGSR) is employed in industry to obtain high-purity H-2 from syngas, where H2O adsorption is an important step that controls H2O dissociation in WGSR. Therefore, exploring catalysts exhibiting strong H2O adsorption energy (E-ads) is crucial. Also, high-entropy alloys (HEA) are promising materials utilized as catalysts, including in WGSR. The PtPd-based HEA catalysts are explored via density functional theory (DFT) and Gaussian process regression. The input features are based on the microstructure data and electronic properties: d-band center (epsilon(d)) and Bader net atomic charge (delta). The DFT calculation reveals that the epsilon(d) and delta of each active site of all HEA surfaces are broadly scattered, indicating that the electronic properties of each atom on HEA are non-uniform and influenced by neighboring atoms. The strong H2O-active-site interaction determined by a highly negative E-ads is used as a criterion to explore good PtPd-based WGSR catalyst candidates. As a result, the potential candidates are found to have Co, Ru, and Fe as an H2O adsorption site with Ag as a neighboring atom, that is, PtPdRhAgCo, PtPdRuAgCo, PtPdRhAgFe, and PtPdRuAgFe.
24.	Somdee, Siriwimol, et al. (författare) First-Principles Investigations on Effects of B-Site Substitution (B-Mn, Fe, and Co) on La-Based Perovskite Oxides As Bifunctional Electrocatalysts for Rechargeable Metal-Air Batteries 2024 Ingår i: Advanced Theory and Simulations. - : WILEY-V C H VERLAG GMBH. - 2513-0390. Tidskriftsartikel (refereegranskat)abstract The effects of B-site substitution (BMn, Fe, and Co) in La-based perovskite oxides (LPOs); LaMnO3, LaFeO3, LaCoO3, as bifunctional electrocatalysts during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in metal-air batteries (MABs) under an alkaline electrolyte (pH = 13) are investigated using density functional theory (DFT). It is found that LaMnO3 exhibits higher ORR activity than others with ORR overpotential (eta ORR) of 0.57 V, but its OER activity is poor with OER overpotential (eta OER) of 1.12 V. The eta ORR (0.59 V) and eta OER (1.13 V) of LaMn0.75Fe0.25O3 closely resemble those of LaMnO3, suggesting that Fe substitution does not yield appreciable enhancements in activity. Fe substitution reduces the ORR and OER activity because the adsorption energies of intermediate species on Fe-substituted LPOs surfaces are too strong to obtain a potential determining step for ORR and OER. According to Sabatier's principle, the LaMn0.25Co0.75O3 demonstrates superior OER activity compared to the other composition, while ORR activity approximates that of LaMnO3, evidenced by eta ORR of 0.65 V and eta OER of 0.53 V. The Co-terminated LaMn0.25Co0.75O3 shows bifunctional activity higher than Mn/Co termination, indicating that Co is an active site for OER and Mn is a promoter for improved ORR activity. The effects of B-site substitution (BMn, Fe, and Co) on La-based perovskite oxides during oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are investigated via density functional theory. LaMn0.25Co0.75O3 as a promising bifunctional electrocatalyst exhibits ORR/OER overpotentials of 0.65 V/0.53 V due to the presence of Mn and Co promoting electron transfer. image
25.	Uchman, Mariusz, et al. (författare) Nonclassical Hydrophobic Effect in Micellization : Molecular Arrangement of Non-Amphiphilic Structures 2018 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 1:1 Tidskriftsartikel (refereegranskat)abstract Micellization brought about by nonclassical hydrophobic effect invokes enthalpy as the driving force. Thus, the underlying molecular phenomena differ from the entropically dominated hydrophobic effect. In quest for a molecular-scale understanding, we report on the molecular arrangement of nonamphiphilic structures of an anionic boron cluster compound, COSAN. We synergistically combine experimental (NMR and calorimetry) and theoretical (molecular dynamics and quantum chemical calculations) approaches. The experimental data support the mechanism of closed association of COSAN, where the self-assembly is driven by the enthalpy contribution to the free energy. Molecular dynamics simulations in explicit solvent show that water molecules form a patchy network around COSAN molecules, giving rise to the strong hydrophobic self-association. In the second solvation shell, water forms a slightly hydrophilic “spot” close to the C-H segments of the cluster. The simulations further show a counterintuitive short-range [COSAN]−∙∙∙[COSAN]− attraction and Na+∙∙∙[COSAN]− repulsion. Quantum chemical calculations reveal a major role of solvation in stabilizing the contact pairs. Further, the calculations show the parallel/X-shape geometrical arrangements of COSAN dimers as the most preferred. Lastly, dihydrogen bonding are found to influence the structure of micelles. In summary, we provide a molecular view of nonclassical micellization that can be extended to other amphiphiles like boranes.
26.	Wangphon, Chanthip, et al. (författare) How Can the PtPd-Based High-Entropy Alloy Triumphs Conventional Twc Catalyst During the NO Reduction? A Density Functional Theory Study 2023 Ingår i: Advanced Theory and Simulations. - : WILEY-V C H VERLAG GMBH. - 2513-0390. Tidskriftsartikel (refereegranskat)abstract Density functional theory is used to compare the catalytic performance of PtPdRhFeCo(100) high entropy alloy (HEA) three-way catalyst (TWC) to the conventional Pt(100) in the NO reduction step during NH3 production that supplies to passive NH3-SCR. Stronger adsorption of NO on the HEA(100) surface is beneficial to capture NO. During adsorption, the catalyst surface acts as an electron donor while the adsorbate is the acceptor on both HEA(100) and Pt(100) systems. Herein, the reaction mechanism of NO reduction can be classified into two steps: 1) NO activation and 2) product formation. During NO activation, direct NO dissociation is the preferable pathway on both HEA(100) and Pt(100) surfaces with the same Ea, whereas HNO and NOH pathways on HEA(100) are suppressed. For NH3, N2, and N2O production on HEA(100) is found to be more difficult than on Pt(100). However, the thermodynamic driving force of all reactions on HEA(100) is more spontaneous than on Pt(100). Also, the rate-determining step on HEA(100) is found to be NH3 formation different from the Pt(100), while difficult H diffusion on HEA(100) is the key factor that reduces NH3 production.
27.	Ångqvist, Mattias, 1989, et al. (författare) ICET - A Python Library for Constructing and Sampling Alloy Cluster Expansions 2019 Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 2:7 Tidskriftsartikel (refereegranskat)abstract Alloy cluster expansions (CEs) provide an accurate and computationally efficient mapping of the potential energy surface of multi-component systems that enables comprehensive sampling of the many-dimensional configuration space. Here, integrated cluster expansion toolkit (ICET), a flexible, extensible, and computationally efficient software package, is introduced for the construction and sampling of CEs. ICET is largely written in Python for easy integration in comprehensive workflows, including first-principles calculations for the generation of reference data and machine learning libraries for training and validation. The package enables training using a variety of linear regression algorithms with and without regularization, Bayesian regression, feature selection, and cross-validation. It also provides complementary functionality for structure enumeration and mapping as well as data management and analysis. Potential applications are illustrated by two examples, including the computation of the phase diagram of a prototypical metallic alloy and the analysis of chemical ordering in an inorganic semiconductor.

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