First-principles Prediction Research Articles

The first-principles prediction of mechanical, electronic, elastic and thermodynamic properties of Mo2XB2 (X=Nb, Os, Ta)

The mechanical, electronic and elastic properties of Mo2XB2 (X = Nb, Os, Ta) at different pressures (0–50 GPa) were predicted using first-principles calculations. The enthalpy of formation and the elastic constant calculations show that the three transition metal borides are thermodynamically and mechanically stable. The analysis of density of state and band structure reveals that Mo2XB2 (X = Nb, Os, Ta) have metallic and covalent properties. The increase of pressure will increase the elastic modulus of Mo2XB2 (X = Nb, Os, Ta). The elastic modulus of Mo2XB2 (X = Nb, Os, Ta) are anisotropic. Furthermore, the quasi-harmonic Debye model is used to predict thermodynamic parameters at various temperatures (0–1200K) and pressures (0–50 GPa), such as heat capacity at constant pressure, heat capacity at constant volume, coefficient of thermal expansion, Debye temperature, and the Grüneisen parameter.

First-principles prediction of Ni-MoO3 as selective and sensitive sensor for detecting CO over CH4, H2, H2O, NH3, H2S gases

First-principles prediction of Ni-MoO3 as selective and sensitive sensor for detecting CO over CH4, H2, H2O, NH3, H2S gases

First-principles prediction of high carrier mobility for β-phase MX2N4 (M = Mo, W; X = Si, Ge) monolayers

The recently synthesized monolayer MoSi2N4 (Science 2020, 369, 367) exhibits exceptional environmental stability, a moderate band gap, and excellent mechanical properties, presenting exciting opportunities for the exploration of two-dimensional (2D) MX2Z4 materials. However, the low carrier mobility of α-phase MoSi2N4 significantly limits its potential applications in field-effect transistor (FET) devices. In this study, we systematically investigate the structural stability, elastic properties, and carrier mobility of a novel family of β-phase MX2N4 (M = Mo, W; X = Si, Ge) monolayers through first-principles calculations. Our findings reveal that these β-phase MX2N4 monolayers demonstrate remarkable dynamic, thermal, and mechanical stability. Specifically, we identify the MoSi2N4, MoGe2N4, WSi2N4, and WGe2N4 monolayers as semiconductors with band gaps of 2.70 eV, 1.57 eV, 3.12 eV, and 1.93 eV, respectively, as calculated using the HSE06 functional. Moreover, the MX2N4 monolayers exhibit significant elastic anisotropy, characterized by high ideal tensile strengths and a critical tensile strain exceeding 25%. Notably, the WGe2N4 monolayer displays exceptional anisotropic in-plane charge transport, achieving mobility levels of up to 104 cm2V− 1S− 1, surpassing those of the α-phase MX2N4 monolayers. These novel ternary monolayer structures have the potential to broaden the 2D MX2Z4 material family and emerge as promising candidates for applications in field-effect transistors.

First-principles prediction of a novel superhard orthorhombic carbon allotrope with large bandgap

First-principles prediction of a novel superhard orthorhombic carbon allotrope with large bandgap

Magnetic Co2Si monolayer with high performance hydrogen evolution reaction: a first-principle prediction

Magnetic Co2Si monolayer with high performance hydrogen evolution reaction: a first-principle prediction

First-principles predictions: exploring semiconductor properties of BeXAs2 (X=Ge and Sn) for photovoltaic applications

In the course of this investigation, we performed ab initio calculations. The investigation systematically explored the physical features of chalcopyrite-phase BeXAs2 (X=Sn and Ge). Total energy calculations incorporated the Wu-Cohen generalized gradient approximation (WC-GGA) [1] to consider the exchange-correlation potential. The analysis of band structures employed the modified Becke Johnson (mBJ) [2] potential approximation, renowned for its effectiveness in addressing concerns related to band gaps. The optical properties of these materials were further elucidated through the determination of the dielectric function and absorption coefficient. The analysis of electronic and optical characteristics underscores the potential applications of BeXAs2 compounds in photonics, optoelectronics, and photovoltaics. Notably, the results exhibit strong agreement with both prior theoretical investigations and experimental data.

General Theory for Longitudinal Nonreciprocal Charge Transport.

The longitudinal nonreciprocal charge transport (NCT) in crystalline materials is a highly nontrivial phenomenon, motivating the design of next generation two-terminal rectification devices (e.g., semiconductor diodes beyond PN junctions). The practical application of such devices is built upon crystalline materials whose longitudinal NCT occurs at room temperature and under low magnetic field. However, materials of this type are rather rare and elusive, and theory guiding the discovery of these materials is lacking. Here, we develop such a theory within the framework of semiclassical Boltzmann transport theory. By symmetry analysis, we classify the complete 122magnetic point groups with respect to the longitudinal NCT phenomenon. The symmetry-adapted Hamiltonian analysis further uncovers a previously overlooked mechanism for this phenomenon. Our theory guides the first-principles prediction of longitudinal NCT in multiferroic ϵ-Fe_{2}O_{3} semiconductor that possibly occurs at room temperature, without the application of external magnetic field. These findings advance our fundamental understandings of longitudinal NCT in crystalline materials, and aid the corresponding materials discoveries.

Investigating nanostructure-property relationship of WTaVCr high-entropy alloy via machine learning optimized reactive potential

In spite of the promising prospects of the WTaVCr refractory high-entropy alloy (RHEA), the nanoscale structure-property relationship remains largely unexplored. This study introduces a supervised machine learning (ML) framework to develop a charge-transfer ionic potential (CTIP) for the W/Ta/V/Cr/O multi-component system. This novel approach demonstrates exceptional advantages in optimizing numerous parameters of a highly flexible yet physically rigorous potential, leveraging a modified distributed breeder genetic algorithm (DBGA) to balance search comprehensiveness and efficiency. The robustness of developed potential is verified through cross-validation against first-principles predictions on various properties of metals, alloys and oxides. Subsequently, dynamic simulations of annealing, mechanical loading, surface oxidation and radiation collision are conducted utilizing CTIP. Results of these simulations align with previous experiments about nanoscale chemical ordering, plastic deformation behavior, oxidation mechanisms and radiation tolerance. These findings not only further corroborate the reliability of CTIP potential, but also uncover atomic-scale insights that are experimentally unattainable, thereby enhancing the understanding of the nanostructure-property relationship.

Untangling individual cation roles in rock salt high-entropy oxides

We unravel the distinct role each cation plays in phase evolution, stability, and properties within the Mg1/5Co1/5Ni1/5Cu1/5Zn1/5O high-entropy oxide (HEO) by integrating experimental findings, thermodynamic analyses, and first-principles predictions. Our approach is through sequentially removing one cation at a time from the five-component high-entropy oxide to create five four-component derivatives. Bulk synthesis experiments indicate that Mg, Ni, and Co act as rock salt phase stabilizers whereas only Mg and Ni enthalpically enhance single-phase rock salt stability in thin film growth; synthesis conditions dictate whether Co is a rock salt phase stabilizer or destabilizer. By examining the competing phases and oxidation state preferences using pseudo-binary phase diagrams and first-principles calculations, we resolve the stability differences between bulk and thin film for all compositions. We systematically explore HEO macroscopic property sensitivity to cation selection employing both predicted and measured optical spectra. This study establishes a framework for understanding high-entropy oxide synthesizability and properties on a per-cation basis that is broadly applicable to tailoring functional property design in other high-entropy materials.

Advancing first-principles dielectric property prediction of complex microwave materials: an elemental-unit decomposition approach

Tungsten-bronze-type material Ba6-3xRE8+2xTi18O54, (RE = rare earth elements) is an important microwave dielectric that has shown great promises for future miniaturization of microwave devices because of its high dielectric constant, low loss, and tunabilities, and there is still much room for improvement. With their proven predictive power, first-principles calculations may greatly help accelerate materials optimization by reducing or eliminating the expensive and time-consuming experimental trial-and-error process. However, microwave dielectrics such as the tungsten-bronze-type materials are rather complex systems with unit cells containing hundreds or thousands of atoms, making ab initio calculations prohibitively expensive. In this work, we propose an elemental-unit decomposition (EUD) technique that can drastically reduce the computational effort of predicting the properties of complex microwave dielectrics and demonstrate its accuracy and efficiency. Our approach facilitates first-principles prediction and design of complex microwave dielectric materials that would otherwise be extremely difficult.

(Invited) Extended Hubbard Functionals for Accurate Modeling of Li-Ion Battery Cathode Materials

Designing novel cathode materials for Li-ion batteries necessitates accurate first-principles predictions of their properties. Density-functional theory (DFT) employing standard (semi-)local functionals encounters challenges due to pronounced self-interaction errors within the partially filled d shells of transition-metal (TM) elements. Here, we demonstrate the efficacy of DFT with extended Hubbard functionals in accurately predicting the "digital" change in oxidation states of TM ions for mixed-valence phases at intermediate Li concentrations in phospho-olivine and spinel cathode materials. The resulting voltages exhibit remarkable agreement with experimental data [1,2].Our approach involves the use of onsite U and intersite V Hubbard parameters computed from density-functional perturbation theory with Lowdin-orthogonalized atomic orbitals, thus circumventing empirical factors [3,4]. Notably, the incorporation of intersite Hubbard V interactions proves indispensable for the precise prediction of thermodynamic quantities, particularly when electronic localization occurs amid inter-atomic orbital hybridization.Extending our investigation to vibrational spectroscopy, we calculate Raman spectra for these materials and find very good agreement with available experimental data [5]. Leveraging the robust and accurate computational framework based on extended Hubbard functionals, we embark on a high-throughput screening of Li-containing compounds, aiming to unveil novel and promising candidates for cathodes [6]. Our findings underscore the pivotal role of advanced DFT methodologies in advancing the discovery and design of high-performance battery materials.[1] I. Timrov, F. Aquilante, M. Cococcioni, N. Marzari, PRX Energy 1, 033003 (2022).[2] I. Timrov, M. Kotiuga, N. Marzari, Phys. Chem. Chem. Phys. 25, 9061 (2023).[3] I. Timrov, N. Marzari, M. Cococcioni, Phys. Rev. B 98, 045141 (2021).[4] I. Timrov, N. Marzari, M. Cococcioni, Phys. Rev. B 103, 085127 (2018).[5] L. Bastonero, N. Marzari, I. Timrov, in preparation.[6] C. Malica, L. Bastonero, M. Bercx, N. Marzari, I. Timrov, in preparation.

First-principles prediction of point defect energies and concentrations in the tantalum and hafnium carbides

First-principles calculations are combined with a statistical–mechanical model to predict the equilibrium point-defect concentrations in the refractory carbides TaC and HfC as a function of temperature and chemical composition. Several different types of point defects (vacancies, interstitials, antisite atoms) and their clusters are treated in a unified manner. The defect concentrations either strictly follow or can be closely approximated by Arrhenius functions with parameters predicted by the model. The model is general and applicable to other carbides, nitrides, borides, or similar chemical compounds. Implications of this work for understanding the diffusion mechanisms in TaC and HfC are discussed.

First-principles predictions of HfO2-based ferroelectric superlattices

The metastable nature of the ferroelectric phase of HfO2 is a significant impediment to its industrial application as a functional ferroelectric material. In fact, no polar phases exist in the bulk phase diagram of HfO2, which shows a dominant non-polar monoclinic ground state. As a consequence, ferroelectric orthorhombic HfO2 is stabilized either kinetically or via epitaxial strain. Here, we propose an alternative approach, demonstrating the feasibility of thermodynamically stabilizing polar HfO2 in superlattices with other simple oxides. Using the composition and stacking direction of the superlattice as design parameters, we obtain heterostructures that can be fully polar, fully antipolar or mixed, with improved thermodynamic stability compared to the orthorhombic polar HfO2 in bulk form. Our results suggest that combining HfO2 with an oxide that does not have a monoclinic ground state generally drives the superlattice away from this non-polar phase, favoring the stability of the ferroelectric structures that minimize the elastic and electrostatic penalties. As such, these diverse and tunable superlattices hold promise for various applications in thin-film ferroelectric devices

A first-principles prediction of novel Janus ZrGeZ3H (Z = N, P, and As) monolayers: Raman active modes, piezoelectric responses, electronic properties, and carrier mobility.

In this article, an attempt is made to explore new materials for applications in piezoelectric and electronic devices. Based on density functional theory calculation, we construct three Janus ZrGeZ3H (Z = N, P, and As) monolayers and study their stability, piezoelectricity, Raman response, and carrier mobility. The results from phonon dispersion spectra, ab initio molecular dynamics simulation, and elastic coefficients confirm the structural, thermal, and mechanical stability of these proposed structures. The ZrGeZ3H monolayers are indirect band gap semiconductors with favourable band gap energy of 1.15 and 1.00 eV for the ZrGeP3H and ZrGeAs3H, respectively, from Heyd-Scuseria-Ernzerhof functional method. It is found that the Janus ZrGeZ3H monolayers possess both in-plane and out-of-plane piezoelectric coefficients, revealing that they are potential piezoelectric candidates. In addition, the carrier mobilities of electrons and holes along transport directions are anisotropic. Notably, the ZrGeP3H and ZrGeAs3H monolayers have high electron mobility of 3639.20 and 3408.37 cm2 V-1 s-1, respectively. Our findings suggest the potential application of the Janus ZrGeZ3H monolayers in the piezoelectric and electronic fields.

Interface structure of α-Mg/14H-LPSO: First-principles prediction and experimental study

The interfacial structure of the α-Mg/14H-LPSO phase in rare earth-including magnesium alloy was investigated via high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and first-principles calculations of density-functional theory. Eleven possible interfacial models were constructed according to the different terminations of the LPSO phase, and the corresponding interfacial energies were calculated, from which the four most stable structures (Ter1-MgY-hollow, Ter2-Zn-hollow, Ter3-MgYII-hollow and Ter4-Mg-bridge) were obtained. The interfacial phase diagrams related to the Y chemical potentials were obtained from the calculations, and the most stable interfacial structure was evaluated. Ter1-MgY-hollow and Ter2-Zn-hollow have the lowest interfacial energies in the range of −0.7 eV < ΔμY < −0.6 eV, where fluctuating change of state is the minimized and the interface is the most stable. The separation work of the two models was calculated to predict the bonding strength of the structures at both ends of the interface. The calculation results show that the maximum interfacial separation work is 1.45 J/m2 for the interface model of α-Mg and 14H-LPSO phase structure with Ter2-Zn-hollow termination.

First-principles predictions of structure, half-metallic antiferromagnetism, optoelectronic, and elastic properties of double perovskites A2TaNiO6 (A = Ca, Sr, and Ba) for energy harvesting

In this article, the electronic, half-metallic antiferromagnetism, and optical characteristics of A2TaNiO6 (A = Ca, Sr, and Ba) double perovskites have been investigated by using WIEN2k code with the GGA + PBEsol approximation. The cubic phase structures were optimized with minimum ground state energy. The electronic attributes showed a semiconductor nature for spin-up channels and a metallic nature for spin-down channels, indicating half-metallicity. Magnetic properties have demonstrated the magnetic moments and antiferromagnetic nature of the studied perovskites. The optical response was assessed by examining dielectric function, absorption coefficient, reflectivity, and energy loss function. Higher values of these parameters in the energy range of 2–4 eV suggest their potential for optoelectronics. Mechanical properties have been also investigated which demonstrated that these compounds have outstanding mechanical stability, anisotropy, mechanical strength, and ductility. The collective results reveal the importance of the analyzed compounds as promising candidates for spintronics, photovoltaics in space, UV-photodetectors, and other UV-based optoelectronic applications.

First-principles prediction of the Co–Al phase diagram including configurational, vibrational and magnetic contributions

Co-based superalloys have attracted attention to replace Ni-based superalloys in high temperature structural applications because of their higher melting temperature and corrosion resistance. Strengthening is provided by Co3(Al, X) (X = W, Cr, Mo, Ni) phases and optimization of their properties requires detailed information about the free energies of the different phases and of the phase diagram of the Co–Al system. This is achieved in this paper through first principles calculations in combination with statistical mechanics. Configurational entropic contributions to the free energy were included through Monte Carlo simulations using the cluster expansion formalism. The vibrational entropy of each phase was determined through the length-stiffness relationship while the magnetic entropy was also included through the Heisenberg Hamiltonian. The computed phase diagram is compared with the currently accepted experimental phase diagram and the different contributions to the stability of each phase are analyzed independently. The potential of this strategy to predict phase diagrams of magnetic systems is clearly established.

Realization of 2D multiferroic with strong magnetoelectric coupling by intercalation: a first-principles high-throughput prediction

The discovery of novel two-dimensional (2D) multiferroic materials is attractive due to their potential for the realization of information storage and logic devices. Although many approaches have been explored to simultaneously introduce ferromagnetic (FM) and ferroelectric (FE) orders into a 2D material, the resulting systems are often plagued by weak magnetoelectric (ME) coupling or limited room-temperature stability. Here, we present a superlattice strategy to construct non-centrosymmetric AM2X4 multiferroic monolayers, i.e., intercalating transition metal ions (A) into the tetragonal-like vacancies of transition metal dichalcogenide bilayers (MX2). Starting from 960 intercalated AM2X4 compounds, our high-throughput calculations have identified 21 multiferroics with robust magnetic order, large FE polarization, low transition barrier, high FE/FM transition temperature, and strong ME coupling. According to the origin of magnetism, we have classified them into twelve type-a, seven type-b, and two type-c multiferroics, which exhibit different ME coupling behavior. During the switching of polarization, the reversal of skyrmions chirality, the transition of the magnetic ground state from FM to antiferromagnetic, and the changes in spin-polarized electron distribution were observed in type-a, type-b, and type-c 2D multiferroic materials, respectively. These results substantially expand the family of 2D ferroic materials and pave an avenue for designing and implementing nonvolatile logic and memory devices.

Predicting the Color Polymorphism of ROY from a Time-Dependent Optimally Tuned Screened Range-Separated Hybrid Functional.

Polymorphism is a well-known property of molecular crystals, which allows the same molecule to form solids with several crystalline structures that can differ significantly in physical properties. Polymorphs that possess different optical absorption properties in the visible range may exhibit different perceived colors, a phenomenon known as color polymorphism. One striking example of color polymorphism is given by 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, known as ROY for its red-orange-yellow colors. First-principles prediction of color polymorphism may help in polymorph assignment and design but has proven to be challenging. Here, we predict the absorption spectra and simulate the colors of 12 ROY polymorphs using the general, nonempirical method of time-dependent (TD) optimally tuned screened range-separated hybrid (OT-SRSH) functional. For 5 ROY polymorphs with known experimental absorption spectra, we show that the TD-OT-SRSH approach predicts absorption spectra in quantitative agreement with experiment. For all polymorphs, we show that an accurate simulation of the colors is obtained, paving the way to a fully predictive, low-cost calculation of color polymorphism.

First-Principles Prediction on Structural, Elastic, Mechanical, and Electronic Properties of Chalcogenide Perovskite CaZrS3 under Pressure

First-Principles Prediction on Structural, Elastic, Mechanical, and Electronic Properties of Chalcogenide Perovskite CaZrS3 under Pressure