First-principles Calculation Method Research Articles

First-principles calculation of ZrS2 as anode material of aluminium ion battery

Developing low-cost, high-stability, and high-performance new ion battery anode materials is beneficial for the rapid development of ion batteries in fields such as rail transit, electronic products, and aerospace. In this work, the first-principles calculation method was used to study the feasibility of ZrS2 monolayer as an anode material for Al ion batteries. The Al ions adsorbed in the strain system tend to bind to the ZrS2 monolayer. In the adsorption system, the adsorption of Al increases the conductivity of the system. The theoretical specific capacity of Al under full load is 690.303 mAh/g. The average open circuit voltage (OCV) is calculated to be 0.635 V. The diffusion barrier of Al ions is 0.071 eV. ZrS2 monolayer is an attractive anode material for ion batteries.

First-principles study of hydrogen trapping and diffusion mechanisms in vanadium carbide with connecting carbon vacancies

Understanding the trapping and diffusion mechanism of hydrogen in vanadium carbide (VC) precipitates is crucial for exploring the issue of hydrogen embrittlement in steel. Although there is widespread consensus that VC can trap hydrogen, the mechanism by which hydrogen diffuses into VC is still unclear. In this study, we used first-principles calculation methods to study the influence of different spacings of carbon vacancies on the trapping and diffusion of hydrogen in VC. The increase in the number of C vacancies makes it easier for vacancies to trap hydrogen, and hydrogen tend to fill up C vacancies. The diffusion of hydrogen into VC only occurs via neighboring C vacancies at a distance of 0.295 nm (connecting vacancies), leading to a diffusion barrier of 0.63–0.78 eV. This is consistent with experimental results and validates the experimental speculation that the diffusion of hydrogen in VC requires a connecting C vacancy grid.

First-principles study on impact of Mo doping on the formation enthalpy and electronic structure of Li2MgN2H2 material

The influence of Mo doping on the formation enthalpy and electronic structure of Li2MgN2H2 material, as well as the specific improvement mechanism of its hydrogen storage properties, were investigated by employing the first-principles calculation method. The calculation results exhibit that when Mo is doped into the Li2MgN2H2 material, it is more inclined to take up Mg lattice site at the 8c position. For the Li2MgN2H2 material, Mo doping can effectively reduce its formation enthalpy by ca. 91.16 kJ/mol, thus resulting in the reduction of its structural stability. Moreover, when the Li2MgN2H2 material is doped with Mo, its cell volume increases, and its band gap narrows obviously. Meanwhile, the strong force between Mo and N causes the bond strengths of N–H and Li–N to weaken significantly. The aforementioned factors are beneficial to the improvement of its hydrogen sorption kinetics. This work aims to provide theoretical guidance for further development of new efficient catalysts to promote the Li–Mg–N–H material's application.

Studying the optical and electronic properties of Eu-doped CdSe phosphors using first principles calculations incorporating the spin orbit coupling method of DFT

We studied the electronic and optical properties of pure and Eu-doped CdSe phosphor materials using the first-principles calculation method, which is a feature of Density Functional Theory. The FP-LAPW method was employed for the study as incorporated in the Wien2k code. The GGA + U + SOC method of DFT was used for the first time in our study to investigate the electronic as well as optical characteristics of Eu-doped CdSe materials. Eu doping was done in two different ratios to study the effects of altered dopant concentration. The doping increased the band gap of the pure CdSe parental material. The calculated band gaps in our study were 0.42 eV for pure CdSe, 0.67 eV for a single Eu atom doped in CdSe, and 1.64 eV for two Eu atoms doped in CdSe. The measured electronic and optical characteristics of undoped i.e, pure CdSe and Eu-doped CdSe showed that the doping significantly changed the optical behavior of CdSe, which may be useful for applications in phosphor-converted LEDs.

Theoretical study on arsenene as anode material for magnesium ion battery in rail transit

The development and regulation of high-performance anode materials contribute to the rapid development of ion batteries in rail transit. In this paper, based on the first-principles calculation method of density functional theory, the properties of two-dimensional arsenene materials are regulated by torsional deformation, and the feasibility of torsionally deformed arsenene as an electrode material for magnesium ion batteries is studied. The results show that the arsenene monolayer remains stable after being adsorbed by a single Mg ion. The properties of arsenene are indirect bandgap semiconductors with a band gap of 1.60 eV. In the current research scope, deformation does not change the semiconductor properties of intrinsic arsenene. As the torsion angle increases, the band gap gradually decreases. The Mg-adsorbed arsenene system exhibits quasi-metallic properties with a band gap of 0.07 eV. The torsional deformation transforms the adsorption system into a small band gap semiconductor. The torsion deformation makes the diffusion energy barrier of magnesium ions on the arsenene monolayer only 0.09 eV, which ensures an excellent charge–discharge rate. The research results provide a theoretical basis for the design of magnesium ion batteries in rail transit.

Influence of doping elements X (X= Hf, Zr, Y, Re, Pd, Ir) on the structural stability and tension property of α-Al2O3/PtAl2-S interfaces

Pt-Al coatings are promising materials for protective materials for turbine blades in new-generation aero-engines. Therefore, it is worth noting that the interface stability and tension property between Pt-Al and the oxide layer, prolonging coating service time. However, systematic studies of doping elements effects on interface adhesion of α-Al2O3/PtAl2 with and without impurity S are still lacking. In this paper, the site preference of the six elements (Hf, Zr, Y, Re, Pd, and Ir) in the PtAl2 alloy, effects of doping elements on the interface adhesion and tension properties of the α-Al2O3/PtAl2-S interface are further explored, performing the first-principles calculation method. Considering comprehensively, Y doping has an excellent enhancement effect on the static interface adhesion and dynamic tensile strength, regardless of whether impurity element S exists in the α-Al2O3/PtAl2 interface. This study will provide necessary theoretical guidance for the composition design of Pt-Al coating and the research of new metal protective coating materials.

First-principles study on atomic formation and manganese diffusion in MnS/Mg-Ti-oxide complex inclusions in steel

Mg-Ti oxide/MnS complex inclusions effectively serve as nucleation sites for intragranular ferrite. This study employs first-principles calculation methods to investigate the inducing properties of complex inclusions, including the growth of MnS on Ti oxide, the absorption of Mn atoms by Ti oxide, and the diffusion behavior of Mn atoms within Ti oxide, both untreated and Mg-treated. Ti2O3 indicates the untreated group, while MgTiO3 indicates the Mg-treated group. Computational analysis indicated that MnS is more likely to adsorb and grow on MgTiO3 than on Ti2O3. MnS vertically grows on the O-Mg-Mg surface of MgTiO3. By calculating the dissociation energy, it can be determined that the Mn in the oxide of the MnS/oxide complex inclusions originates from the steel matrix rather than from MnS. By analyzing the diffusion behavior of vacancies and Mn atoms through energy barrier calculations, it is evident that the addition of Mg alters the diffusion pathways of Mn atoms in Ti oxide and confirms that the bonding between Mn and O is the limiting step for Mn atom diffusion within the oxides. The diffusion path of Mn atoms in MgTiO3 is Path I → Path II → Path I. Path I: Mn atoms diffuse within the cationic layer. Path II: Mn atoms diffuse by traversing across two layers of O atoms.

First principles study of V2CT2-based MXenes materials in oxygen reduction and oxygen evolution reactions

The development of bifunctional ORR/OER electrocatalysts with low cost, high activity and sustainable cycle plays an important role in improving the performance of new green energy storage and conversion devices to alleviate the energy crisis and environmental pollution. As a graphene-like two-dimensional inorganic layered compound with unique electrochemistry, MXenes materials have attracted more and more attention in the field of electrocatalytic applications. In this paper, based on the first-principles calculation method based on density functional theory (DFT) and quantum mechanics, an effective scheme for designing efficient ORR/OER bifunctional electrocatalysts by introducing Pd/Pt single atoms to regulate the electronic structure of V2CT2 (T = O, F) is proposed. Firstly, we discussed the stability of the designed series of single-atom catalysts by calculating the formation energy, binding energy and molecular dynamics simulation. Secondly, by comparing the theoretical overpotentials of these single-atom catalysts for ORR and OER, we found that among the designed SACs, V2CO2-Pd, V2CF2-Pd and V2CO2-VO-Pt are catalysts with good bifunctional catalytic activity for ORR/OER. Our work provides some guidance for the application of MXenes materials in the field of electrocatalysis.

The role of oxygen in the growth of silver nanowires using the polyol method

Silver nanowires (Ag NWs) are gaining significant interest as a promising material for applications in flexible electronics. However, the growth mechanism of Ag NWs, particularly during the polyol synthesis process, remains unclear due to the complex reduction pathways of ethylene glycol (EG). In this paper, first-principles calculation method was employed to investigate the influence of oxygen during the growth of Ag NWs. Specifically, oxygen affects the decomposition products of ethylene glycol and thus the reducibility of EG. This research aims to reveal the mechanism of oxygen promoting the growth of Ag NWs.

Study of bond strength and electronic properties at the 6H-SiC/Al interface: Based on first-principles calculations

As the medium between the reinforcement and the matrix, the interface plays a critical role in the mechanical properties of silicon carbide particle reinforced aluminum matrix composites. This study used first-principles calculation methods to systematically analyze 14 different 6H-SiC/Al low-index interfaces, including atomic configuration, interface bonding strength, and electronic structure and bonding principles between interfaces. The adhesion work calculations reveal that the C-top-SiC(0001)/Al (111) and SiC(0001)/Al (100) interfaces have larger adhesion work values, specifically 5.09 J/m2 and 5.021 J/m2, respectively. Additionally, the rigid tensile testing confirms that the tensile stress values at the interfaces of C-top-SiC(0001)/Al (111) and SiC(0001)/Al (100) are higher, measuring 36.4 GPa and 32.5 GPa, respectively. The above results show that the interface bonding strength of these two configurations is the highest, the most stable, and most likely to appear in the 6H-SiC/Al interface configuration. The results of the analysis on charge density difference and partial density of states indicate that the interfaces of C-top-SiC (0001)/Al (111) and SiC (0001)/Al (100) are primarily composed of strong ionic and covalent bonds.

First-principles study on thermal transport properties of GaN under different cross-plane strain

With the development of power devices towards high integration and power, the electrical and thermal stresses per unit area become more concentrated and intensified. The impact of cross-plane strain resulting from inverse piezoelectric effect and thermal expansion on power devices cannot be ignored. Cross-plane strain has a substantial influence on the thermal properties of GaN. However, the research on the influence of cross-plane strain on the thermal conductivity of GaN has not been reported in the literature. Based on the first-principles calculation method and the phonon Boltzmann transport equation, the influence of cross-plane strain on the thermal conductivity and phonon characteristics of the GaN lattice is systematically studied in this study. The thermal conductivity of GaN has anisotropy and increases significantly with the decrease in temperature. The thermal conductivity of GaN at room temperature under the free state is calculated to be 257 and 275 W/(m·K) for in-plane (k⊥) and cross-plane (k∥) directions, respectively. Compared with previous theoretical reports, our calculation results are more consistent with the existing experiment values. Under the state of cross-plane strain, the lattice thermal conductivity changes remarkably. In detail, the average thermal conductivity at room temperature decreased by 35 % under a 5 % cross-plane tensile strain state, while it increased by 11.5 % under a 5 % cross-plane compressive strain state. According to the calculation results, the influence of cross-plane on lattice thermal conductivity is mainly due to the change in phonon lifetime. The analysis of two mechanisms of phonon lifetime suppression indicates that the cross-plane strain will significantly change the frequency of the high-frequency optical acoustic branch. This result leads to a change in the phonon scattering process and thus affects the phonon lifetime. Besides, the anisotropy of thermal conductivity changes under different strain values, which may be due to the weakened piezoelectric polarization effect induced by strain.

Melt growth of crystalline α-SrSi2 by the vertical Bridgman method and its thermoelectric characteristics

As a candidate thermoelectric material operating in the low-temperature regime (room temperature to 473 K), we have examined α-SrSi2: a narrow bandgap semiconductor material, which is composed of environmentally benign elements. We are able to report the successful production of single-crystalline-like α-SrSi2 with clear semiconducting properties by melting synthesis, a thermodynamically stable and thermally equilibrium process that reduces unexpected process contamination and improves crystallinity.The crystals up to 20 × 20 × 5 mm3 have been obtained for a solid–liquid phase reaction temperature of 1308 K for 10 h with a growth rate averaging at 0.617 K/h in the temperature range from 1403 K to 1373 K. The band gap of this material was measured at 48 meV, which is higher than the values previously reported. The power factor was measured at 2.9 mW/mK2 at 300 K, which is the highest value ever reported for undoped α-SrSi2.Based on the experimental bandgap values, the hybrid functional was used to correct the first-principles calculation method, and the Seebeck coefficient obtained from the first-principles calculation was compared with experimental values. Which values showed good agreement with experimental values.

Atomic-scale tribological behavior of pressure-induced MoO3(0 1 0)/Ag(1 1 1) heterogeneous sliding interface

The atomic-scale tribological properties of the MoO3(010)/Ag(111) heterogeneous sliding interface were studied by first-principles calculation method. The interface binding energy, sliding potential energy, friction force, charge density difference, partial density of states, Mulliken bond population and HiRshfeld charge were analyzed, and the essence of the friction was revealed. The results show that the sliding potential energy and friction exhibit anisotropy for the pressure-induced MoO3(010)/Ag(111) heterogeneous sliding interface. The friction force can be described by the change of the sliding potential energy, and the charge redistribution between interface atoms is the intrinsic reason for the change of tribological properties. This work provides atomic and electronic level insights for understanding the tribological characteristics between two-dimensional materials and soft metals.

First-Principles Calculations of TiB4 and TiB5 as Anodes with High Capacity for Na-Ion Batteries.

The electrochemical properties of TiB4 and TiB5 monolayers in Na-ion batteries (NIBs) were studied by using the first-principles calculation method based on density functional theory. The TiB4/TiB5 monolayer showed excellent Na storage capacity, capable of adsorbing two layers of Na with theoretical capacities of 1176.77 and 1052.05 mA g-1, respectively. The average operating voltages of the TiB4 and TiB5 monolayers are 0.073 and 0.042 eV, respectively, indicating that they can be used as anode materials for NIBs. More interestingly, the exposed B surface not only brings a high theoretical capacity but also provides a relatively small diffusion barrier of 0.16 (for TiB4) and 0.33 eV (for TiB5), enhancing their rate capability in NIBs.

First-principles calculations of the electronic structure and thermodynamic properties of B–Co–O materials

In the present study, the structural properties, electronic, elastic, and thermodynamic properties of Co4B6O13、Co2B2O5、Co3(BO3)2、Co(BO2)2, and CoB4O7 materials were calculated by adopting first-principles calculation method based on density functional theory. The simulated lattice constant is compliant with the existing experimental data well. The formation energy, Gibbs free energy, and phonon dispersion curves show that the B–Co–O materials are thermodynamically stable. The results show that the mechanical properties of CoB4O7 material is excellent, while the mechanical properties of Co2B2O5 material is the weakest. The CoB4O7 material has higher Debye temperature and constant volume heat capacity, and the thermodynamic stability of Co3(BO3)2 is the best. By analyzing band structure and electronic density of states, Co2B2O5 and Co3(BO3)2 materials are conductors, Co4B6O13, Co(BO2)2 and CoB4O7 materials belong to P-type semiconductors. Through electronic density of states analysis and Hirshfeld analysis, they indicated that five B–Co–O materials exhibit ferromagnetic.

Efficient visible-light-driven photocatalytic hydrogen evolution in novel type-II SnS2/Al2S2 van der Waals heterostructures

With the exacerbation of environmental pollution and the energy crisis, the development and design of environmentally friendly and efficient photocatalytic catalysts for water splitting with visible light have become particularly imperative. This study delves into the detailed investigation of the novel type-II van der Waals heterostructure of SnS2/Al2S2 utilizing first-principles calculation methods. By leveraging the advantages of indirect type-II band alignment and high carrier mobility, the efficient separation of electron-hole pairs is achieved, thereby facilitating enhanced participation of electrons and holes in photocatalytic reactions. Furthermore, the heterostructure manifests a peak optical absorption coefficient value of approximately 5.34×104 cm−1 in the visible light spectrum, accompanied by the occurrence of red-shifting, which fosters efficient absorption of visible light. It is noteworthy that under conditions of pH = 0–3.7, the heterojunction surpasses the redox potential of water splitting, concurrently displaying a substantial hydrogen evolution reaction (HER) and a high efficiency of converting sunlight to hydrogen (22.31 %). These results underscore the promising potential of the SnS2/Al2S2 heterostructure as a photocatalyst for water splitting, offering crucial theoretical support and practical guidance for the further advancement of hydrogen production via water splitting technology.

Thermal Transport Properties of Two-Dimensional Janus MoXSiN2 (X = S, Se, and Te).

The design of Janus materials offers an effective means of regulating both their physical and chemical properties, leading to their application in various fields. However, the underlying mechanism governing the modulation of the thermal transport characteristics through the construction of Janus materials remains unclear. In this work, we introduce VI-group elements into the MoSi2N4 structure, yielding two-dimensional Janus MoXSiN2 (X = S, Se, and Te) and systematically investigate their thermal transport properties based on first-principles calculation methods. Our findings reveal that the lattice thermal conductivities (κl) of MoSSiN2, MoSeSiN2, and MoTeSiN2 are 47.2, 24.3, and 40.6 W/mK at 300 K, respectively, significantly lower than that of MoSi2N4 (224 W/mK). Such low κl values mainly come from the introduction of X atoms, which enhances phonon scattering and reduces phonon vibration frequencies. In addition, MoTeSiN2 exhibits a higher κl compared to MoSeSiN2, contrary to the trend observed in most materials containing VI-group elements, where κl decreases gradually from S to Te. This anomalous behavior can be attributed to the competitive result between its lower phonon vibrational frequency and weaker phonon anharmonicity of MoTeSiN2. This work elucidates the inherent mechanism governing the modulation of thermal transport properties in Janus materials, thereby enhancing the potential application of Janus MoXSiN2 in engineering thermal management.

Effect of solutes segregation in a binary TiAl alloy: A first-principles calculation method

Comprehending the interfacial structures and energetics of interfaces between γ-TiAl and α2-Ti3Al phase is critical to understanding the stabilities of the binary-phase TiAl-Ti3Al alloy. Here a comprehensive first-principles investigation is reported on the structures and energetic properties of γ-TiAl(111)/α2-Ti3Al(0001) interfaces with 19 segregated transition metals considered. The results indicate that all considered atoms have a tendency to segregate at the interface. The interfacial strength enhancement occurs after V, Cr, Mn, Fe, Nb, Mo, Tc, Ru segregated in TiAl, Ag segregated in Ti3Al, and almost all solute atoms can improve interface stability. Compared with the pure interface, the bonding between the segregated atoms and the surrounding atoms is stronger at the interface after V or Nb segregation, while the bonding between Cd and the surrounding atoms is weaker. Our calculations provide the necessary interfacial structures and energetics for predicting the stabilities of binary TiAl alloy.

Effect of non-metal doping on the optoelectronic properties of ZrS2/ZrSe2 heterostructure under strain: a first-principles study.

In this paper, we systematically studied the effects of non-metallic element (B, C, N, O, F) doping and biaxial stretching on the photoelectric properties of ZrS2/ZrSe2 heterostructures by using the first-principles calculation method based on density functional theory. The results show that the p-type doping is realized by B, C, and N atom doping, and the n-type doping is realized by O and F atom doping. The doping of B and C atoms produces impurity energy levels in the band gap, which affects the conductivity of the heterostructure. The band gap of N and O atom-doped heterostructures increases under tensile strain, but it is still a direct band gap. The analysis of the optical properties of the heterostructures shows that the doping of non-metallic atoms can adjust the optical absorption rate and reflectivity of the heterostructures. Under the action of tensile strain, the optical properties of the doped heterostructures have changed significantly in the low-energy region. This article provides a theoretical basis for the future application of ZrS2/ZrSe2 heterostructures. This paper uses the first-principles calculation method based on density functional theory. The PBE exchange-correlation functional based on generalized gradient approximation (GGA) is selected for the specific calculation, and the crystal structure is geometrically optimized by the ultrasoft pseudopotential method. It is verified that when the cutoff energy of the ZrS2/ZrSe2 heterostructure is 500 eV, the K-point grid is selected to be 10 × 10 × 2 with the lowest energy, so the cutoff energy is selected to be 500 eV. The K-point grid is selected to be 10 × 10 × 2. The convergence limits for structural optimization are as follows: the maximum force between atoms is 0.01 eV/Å, the convergence threshold of the maximum energy change is set to 10-9 eV/atom, and the convergence threshold of the maximum displacement is 0.001 Å. In order to avoid the influence of atomic periodic motion between different atomic layers, a vacuum layer of 20 Å is added in the vertical direction. Considering the interaction of vdW between the interfaces, the DFT-D2 method is used to verify. The optical properties were calculated by the random phase approximation method, and the K-point grid was selected as 12 × 12 × 2.

First principles investigation of in-situ NiAl(110)/Ag(111) and NiAl(110)/MoO3(010) heterogeneous interfaces behavior in composite coatings

The interface properties of in-situ NiAl(110)/Ag(111) and NiAl(110)/MoO3(010) heterogeneous interfaces were systematically studied by first-principles calculation method. The interfacial adhesion work, interfacial energy, Mulliken bond population and partial density of states were analyzed, and the bonding mechanism were revealed from the atomic and electronic perspective. The results show that the NiAl(110)/Ag(111) heterogeneous interfaces with OB-NiAl stacking site and the NiAl(110)/MoO3(010) heterogeneous interfaces with OT-Al stacking site are the most stable interface structures with maximum interfacial adhesion work (1.602 J/m2 and 2.833 J/m2, respectively) and minimum interfacial energy (0.7391 J/m2 and −0.8154∼0.7796 J/m2, respectively). Furthermore, charge density differences, partial density of states and Mulliken bond population analysis indicates that the interface bonding mechanism of NiAl (110)/Ag(111) heterogeneous interface is dominated by Al-Ag covalent bonds, and the bonding mechanism of NiAl(110)/MoO3(010) heterogeneous interface is mainly the combination of Al-O ionic bonds and Al-Mo covalent bonds.