Pseudopotential Density Functional Method Research Articles

Contrasting packing modes for tubular assemblies in chlorosomes

The largest light-harvesting antenna in nature, the chlorosome, is a heterogeneous helical BChl self-assembly that has evolved in green bacteria to harvest light for performing photosynthesis in low-light environments. Guided by NMR chemical shifts and distance constraints for Chlorobaculum tepidum wild-type chlorosomes, the two contrasting packing modes for syn-anti parallel stacks of BChl c to form polar 2D arrays, with dipole moments adding up, are explored. Layered assemblies were optimized using local orbital density functional and plane wave pseudopotential methods. The packing mode with the lowest energy contains syn-anti and anti-syn H-bonding between stacks. It can accommodate R and S epimers, and side chain variability. For this packing, a match with the available EM data on the subunit axial repeat and optical data is obtained with multiple concentric cylinders for a rolling vector with the stacks running at an angle of 21° to the cylinder axis and with the BChl dipole moments running at an angle ß ∼ 55° to the tube axis, in accordance with optical data. A packing mode involving alternating syn and anti parallel stacks that is at variance with EM appears higher in energy. A weak cross-peak at -6 ppm in the MAS NMR with 50 kHz spinning, assigned to C-181, matches the shift of antiparallel dimers, which possibly reflects a minor impurity-type fraction in the self-assembled BChl c.

First-principles calculations investigating structural, electronic optical and elastic properties of ABSe3 (A = Rb, Cs) compounds explored for photovoltaic and optoelectronics applications

In few recent years, great and significant efforts are devoted from researcher all over the world to pursue the revolution of photovoltaic’s materials and their uses in various applications. In the present work, a series of ab-initio simulations based on the density functional theory DFT plane wave pseudo-potential (PW-PP) method and hence performed towards the perselenoborate materials ABSe3 (A = Rb,Cs) for the first time along the three main polarizations of the incident wave directions [100], [010] and [001] with the aim of exploring their structural, electronic, optical and elastic properties. The generalized gradient approximation Perdew–Burke–Ernzerhof (GGA-PBE) carried out with CASTEP code is used for the exchange–correlation potential. The computed results showed that the structural properties of investigated compounds are very good agreement to the available experimental data, showing that the current calculations are quite accurate. Moreover, the density of states and electronic band structure calculations reveal that RbBSe3 (CsBSe3) compounds exhibit direct band gap semiconductor nature 1.66 eV (1,82 eV) respectively within the optimal range band gap 1eV–2eV required for photovoltaic’s applications makes them having great potential to obtain efficient Perovskite solar cell PSC. Additionally, our finding optical properties calculations reveal that the two investigated compounds exhibit strong absorption (prominent absorption peaks up 2,4 × 105cm−1) in UV range, while the real part of the refractive index for RbBSe3 (CsBSe3) was 2.62 (2.60) respectively which might be beneficial for photovoltaic application (top cell in solar cell) and optical applications. Also, high optical conductivity (∼1015sec−1) is found to be observed in visible ultraviolet range (1.7 eV to 30 eV). The lower reflectivity seen by RbBSe3 compared to CsBSe3 in the larger energy spectrum of electromagnetic radiation suggests that RbBSe3 compound is more suitable for electronic applications. Further, once the elastic constants are obtained, the calculated mechanical properties, bulk modulus (B), shear modulus (G), the ratio B/G, Young’s modulus (E), Poisson’s ratio (ν), anisotropy universal (AU) are calculated. Our calculated Young’s modulus indicate that the CsBSe3 is less hardness compared to RbBSe3, while Poisson’s ratio calculated leads them to have a character ionic and RbBSe3 is more ductile than CsBSe3. The calculation value of θ D predicted from elastic constants appears low which is closely related to many physical properties such as specific heat and melting temperature. Finally, the finding results reveal another way of investigating mechanical stability, where both compounds are mechanically stable since all elastic constant computed are perfectly satisfied the Born stability criteria, flexible and brittle. Finally, we hope that all these results will be helpful for designing photovoltaic and optoelectronic devices.

Theoretical study of the photocatalytic activity of hBNC/MoSX (X = Se, Te) heterojunctions

The effects of the introduction of C-C bonds on the stability, electronic structure, work function, and optical properties of hBN/MoSX heterojunctions are investigated based on the density functional theory plane wave ultra soft pseudopotential method. The results show that the hBNC/MoSX heterojunctions have low binding energies (−4.066 eV to −4.777 eV) and lattice mismatch ratios (2.62 % and 1.44 %) and can be stabilized at room temperature of 300 K, indicating that they possess excellent stability. By comparing the electronic structure with that of the hBN/MoSX heterojunction, it is found that the introduction of C-C bonds can effectively adjust the band gap of the heterojunction. The bandgap of hBN/MoSX varies from 1.018 eV to 1.168 eV with small variations. The hBNC/SMoSe and hBNC/SMoTe heterojunctions have bandgaps of 0.309 eV and 0.494 eV, with significantly reduced bandgaps and orbital hybridization. The number of electrons in the excited state increases, which makes the electron leap easier and is beneficial to improve the response of the heterojunction to visible light. Due to the presence of the built-in electric field at the interface, the compounding of photogenerated electron-hole pairs can be effectively suppressed, which greatly enhances both the heterojunction photocatalytic ability and carrier migration. Compared with the hBNC monolayer system, both were red-shifted in the low-energy region. hBNC/SMoTe and hBNC/SMoSe showed the best absorption of light in the low-energy region, indicating excellent photocatalytic performance.

Ab-initio study of the optical properties of 2D Yn+1Cn (n = 1, 2, and 3) MXenes and bulk of YC

Calculations are accomplished in the framework of density functional theory and pseudopotential method with local density approximation (LDA) and QUANTUM-ESPRESSO/PWSCF computational code. Large negative values of ε1ω represent that materials exhibit Drude-like behavior while at higher energies, interband transitions occur. According to the results of the imaginary part of the dielectric functionε2ω, it can be stated that the absorption starts from small energies, which indicates that the bulk of YC and Yn+1Cn (n = 1, 2, and 3) monolayers have no energy bandgap and show a metallic nature. The sharp plasmonic energy peak for the YC structure in the x-direction can be seen at 18.61 eV; also the values of sharp plasmonic energy peaks for the Y2C, Y3C2, and Y4C3 in the x-direction are 13.40 eV, 11.98 eV, and 10.14 eV respectively. The results of the reflection spectrum show that the bulk of YC and 2D Yn+1Cn (n = 1, 2, and 3) MXenes have large values due to the presence of free electrons and plasma fluctuations, and confirm the metallic nature of the mentioned compounds. For the bulk of YC, the refractive index prominent peaks approach zero within the photon energy range of 13 eV up to 16 eV, while the corresponding range for the 2D Yn+1Cn MXenes is narrower and equal to 6 eV up to 7 eV. Also, the absorption spectrum in the bulk structure of YC and Yn+1Cn MXenes starts from zero photon energy which verifies the metallic behavior of the studied structures.

First-principles study of the impact of hydrogen on the adsorption properties of Ti-decorated graphdiyne storage methane

Based on density functional theory (DFT) and pseudopotential plane-wave method. CH4 adsorption properties of Ti-decorated graphdiyne (Ti-GDY) when introducing H2 are calculated. The results indicate that Ti-GDY adsorbs 30 CH4 and 6 H2 on the double-side. The storage capacity of CH4 is 63.54 wt%, and the average adsorption energy is - 0.170 eV. H2 biases the polarization direction of CH4 towards the Z-axis (perpendicular to the substrate plane), and accumulates negative charge on the C atom on the substrate to form a negative charge center. Introduction H2 improves the CH4 adsorption properties of Ti-GDY, which is a promising energy storage method.

Structural, elastic, electronic, thermal, and phononic properties of yttrium carbide: First-principles calculations

In this paper, structural, electronic, elastic, phononic, and thermal properties of YC in both rock-salt (B1) and CsCl (B2) phases are studied. Calculations have been performed by using QUANTUM-ESPRESSO/PWSCF computational package which is based on density functional theory (DFT) and pseudo-potential method. Local density approximation (LDA) and generalized gradient approximation (GGA) have been used for modeling the exchange and correlation effects. According to the total energy diagram versus unit cell volume, the YC compound in the B1 phase is more stable than that of the B2 phase at ambient pressure. The computed elastic parameters indicated that the B2 phase did not satisfy the mechanical stability conditions at ambient pressure and is considered to be an unstable phase of the YC structure.The analysis of the enthalpy versus pressure diagram predicts that the structural phase transition from the B1 phase to the B2 phase occurs at pressures 51 GPa and 71.5 GPa, for various LDA and GGA approximations, respectively. Based on the phonon dispersion curves at ambient pressure, the B1 phase of the YC compound is dynamically stable, while at high pressure, the YC compound in the B2 phase has shown stability. Using calculated elastic constants, the small amount of Zener anisotropy factor A shows a strongly anisotropic nature of the YC structure. The higher amount of the calculated Poisson's ratio (~0.40) than that of the corresponding critical value (~0.33) together with the positive values of Cauchy pressure within the LDA and GGA approximations present the ductility and metallic behavior of the YC compound in the B1 phase. The band structure and total density of states calculations also verify the metallic behavior of the YC compound in the stable B1 phase. From PDOS calculations, overlapping the 4d orbital of the Y atom and 2p orbital of the C atom near the Fermi level indicates that these orbitals have significant contributions to the bonding between the Y and C atoms. This bonding is substantiated by the corresponding electron density distribution. The thermodynamic calculations indicated that the heat capacity increases regularly and continuously with the increase in temperature T, toward the classical Dulong-Petit value of 6R for the bulk structure of the YC compound with two atoms in the primitive cell. It can also be predicted for the YC compound that the smaller lattice parameter within the LDA approximation compared to the GGA approximation causes stiffness increases, followed by an increase in the Debye temperature. The increasing trend of entropy versus temperature indicates the endothermic behavior of the YC compound.

Regulated microarchitecture, spin polarization state, and observed charge transfers for cerium boride CeB6 under electrical Field

The thermal stabilities, microarchitectures as well as the electronic states of the cubic CeB6 under electrical field have been systematically investigated in detail within the framework of plane wave pseudo-potential density functional theory calculational method. Specifically, theCeB6 under electrical field of 0.0002 V/Å has lower total energy and enthalpy of formation. The cell of theCeB6 under electrical field is slightly expanded and the lattice expansion is isotropic, along with microarchitecture regulations. The distances between B are 2.523 Å, 1.707 Å and 1.784 Å, showing covalent bonds. There are 5 sub-bands for CeB6, the energy widths of bands are regulated with the conduction band and the first valence band moving downwards under electrical field. There are 3 band valleys and 5 band peaks for the CeB6, with metallic transition and decreased band gaps under electrical field. The middle conduction band and the first valence band are formed by f, d and p orbital electrons, respectively. The Ce s and the B orbital electrons tend to polarize under electrical field. The Ce f, Ce s and B orbital electrons are responsible for the ferrimagnetic magnetism under electrical field. There are charge transfers among these orbitals for CeB6 under electrical field.

Ab-initio study of atomic structure and mechanical behaviour of [formula omitted] intermetallic interfaces

First-principles virtual tensile and shear test calculations have been performed to Al(003¯)//α-AlFeSi(001) and Al(01¯4)//Fe4Al13(101¯) interfaces by the ab initio pseudo potential density functional theory method. Work of separation, ultimate tensile strength and shear strength of bulk and interface structures were calculated. The Al(003¯)/α-AlFeSi(001) interface showed higher tensile strength than the Al(01¯4)//Fe4Al13(101¯) interface structure. Moreover, interface calculations revealed a charge depletion region in the second layer of the Fe4Al13 structure, which caused lower work of separation. Furthermore, shear calculations showed stronger shear strength for the Al(01¯4)//Fe4Al13(101¯) interface than for the Al(001)//α-AlFeSi(001) interface structure.

Quantum-Mechanical Simulation of the Defects Influence on the Shear Rupture in γ-TiAl

The effect of point defects on the shear rupture resistance in titanium aluminide is investigated by the density functional theory and pseudopotential methods. Vacancies, as well as substitution atoms – tungsten and chromium were considered as points defects. The shear was simulated in the(111) slip plane for two directions, namely [110] and [11-2]. It is shown that for a {111}<110> sliding system, vacancies significantly reduce the shear resistance. However, when alloying element occupies a titanium vacancy, it can partially compensate for this negative effect.

A density functional theory analysis of the mechanical and dynamic stability and thermodynamic properties of pyrite-type ZnSe2 and ZnTe2

The present work is the first quantitative theoretical investigation of elastic, dynamical and thermodynamic properties of Zinc diselenide, ZnSe2 and Zinc ditelluride, ZnTe2 based on a density functional theory plane-wave pseudopotential method. The first-principles calculations were carried out using the local density approximation, (LDA) and the generalized gradient approximation, (GGA) of Perdew Burke and Ernzerhof (PBE) in a pyrite-type structure. The structural properties obtained were consistent with existing experimental and theoretical results found with a related approach. The elastic constants were calculated by adopting a stress-strain approach and the mechanical stability of the compounds was established using elastic stability criteria. Both compounds were predicted to be ductile with good plasticity according to Pugh's and Poisson's ratios respectively. Dynamical stability was determined from the calculations of phonon dispersion spectra. ZnSe2 is predicted to be dynamically stable while ZnTe2 stability is open for verification when experimental result is available, this is because LDA predicts dynamically stable compound while PBE proves otherwise. The thermodynamic properties between the temperature range of 0–1000 K were calculated using the computed phonon density of state. There is a monotonic increase in internal energies with temperature the vibrational free energies decreases continually as temperature increases. Sharp increase was observed in specific heat capacity at constant volume between 0 and 400 K while at higher temperature CV gradually approaches the asymptotic limit of 300 J mol−1k−1. The values at ambient temperature were also reported.

High-pressure structure prediction and high-temperature structural stability of periclase

Periclase is the terminal component of the ferropericlase, and its chemical composition is MgO. It is well known that there exists a huge difference between the melting curves of MgO determined experimentally and theoretically. A feasible way to clarify the nature of the melting temperature is to investigate the possible new phase of MgO. Meanwhile, it is very important to study the new phase and the influence of temperature on structural stability of MgO in high-pressure condensed matter physics and geophysics. In the present work, we study in detail the phase stability and the possible existing structures of MgO, which include the structure predicted by particle swarm optimization algorithm through using the first-principles pseudopotential density functional method. We find that MgO crystallizes into a rocksalt structure in a pressure range from 0 to 580 GPa and that the CsCl-type structure is of a high-pressure phase at up to 800 GPa. Although an NiAs-type hexagonal phase perhaps explains the volume discontinuity at (170 ± 10) GPa along the MgO Hugoniot in a shock-compression experiment (Zhang L, Fei Y W 2008 <i>Geophys. Res. Lett</i>. <b>35</b> L13302) and a wurtzite phase perhaps explains the huge difference between the melting curves of MgO determined experimentally and theoretically (Aguado A, Madden P A 2005 <i>Phys. Rev. Lett</i>. <b>94</b> 068501), neither of them is existent in the entire range of pressures studied, according to the thermodynamic stability calculations. The calculations of phonon spectra indicate that the B3, B4, B8<sub>1</sub>, B8<sub>2</sub>, and <i>P</i>3<i>m</i>1 phases of MgO are dynamically stable at zero pressure. That is to say, all of the predicted structures are the metastable structures of MgO. In addition, the high-temperature structural stability of MgO is investigated by using very similar Lewis-Catlow and Stoneham-Sangster shell model potential based on the classical molecular dynamics (MD) simulations. In order to take into account the non-central force in crystal, the breathing shell model is also introduced in simulation. The thermodynamic melting curves are estimated on the basis of the thermal instability MD simulations and compared with the available experimental data and other theoretical results in the pressure range of 0－150 GPa.

Elastic constants and homogenized moduli of manganese carbonate structure based on molecular dynamics and Reuss-Voigt-Hill methods

With the development of computer technology, the crystal structure of atomic-scale dynamics simulation is a hot research in recent years. The manganese carbonate crystal structure is chosen as the research object, as the elasticity of manganese carbonate crystal structure has been studied based on the plane wave ultra-soft first-principles density functional theory framework pseudopotential method. Based on molecular dynamics, interatomic potential function was introduced to describe the interactions between atoms of manganese carbonate crystals and then elasticity contants of manganese carbonate crystals, bulk modulus, shear modulus, Young’s modulus were simulated. Influencing of the pressure on elastic properties has been studied, the results indicate that: 1) the structure of manganese carbonate crystal shows anisotropy due to the different types of atoms of Coulomb force and van der Waals forces; 2) elastic moduli are also obtained, of which the bulk modulus B is 107.682GPa, shear modulus G is 52.09GPa; 3) the values are very consistent to the results of Chen (B 108GPa and G 49.8GPa), thus the established model and the selected potential functions are verified to be reliable.

High-temperature and high-pressure physical properties of CuI with zinc-blende phase by a systematic ab initio investigation

A systematic ab initio investigation has been performed to determine the elastic stability, the structural and finite-temperature thermodynamic properties of copper iodide (CuI) in the zinc-blende phase under pressure. All calculations are carried out based on the pseudopotential density functional method, in which we employ the generalized gradient approximation of the revised Perdew-Burke-Ernzerhof form and local density approximation of Ceperly and Adler parameterized by Perdew and Zunger together with plane-wave basis sets for expanding the periodic electron density. The obtained normalized volume dependence of the pressure and the equation-of-state parameters including equilibrium volume, isothermal bulk modulus and its pressure derivatives are in excellent agreement with the experimental data and other theoretical results. The elastic constants are calculated and the investigation of the mechanical stability from the elastic constants under pressure indicates that the zinc-blende CuI is stable up to 10GPa. Through the careful evaluation with the quasi-harmonic Debye model in which the phononic effects are considered, a complete set of thermodynamic data up to 800K, including the bulk modulus, volume thermal expansion coefficient, heat capacity, entropy, Debye temperature, and Grüneisen parameter of CuI with zinc-blende structure is achieved. This set of data is considered as the useful information to understand the high-temperature and high-pressure properties of CuI.

Microstructure, bonding properties and the basis of pinning effect of in-situ NbC reinforced Co50 composite coating by plasma cladding

One of the vital problems limiting the application of multi-layer cladding coating is that there appears a coarse grain structure at interface between different layers. In order to refine the grain and increase the bonding strength, Nb was added to Co50 composite coating in this study. The multi-layer Co50 composite coating was fabricated by plasma cladding. Microstructure was investigated by scanning electron microscopy (SEM) with energy dispersive spectrum (EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). And the effect of Nb on bonding strength was investigated using tensile test and first-principles calculations based on density functional plane-wave ultrasoft pseudopotential method. The results show that when Nb is added, a few in situ synthesized NbC with very small grain size appears on the grain boundaries, restraining those movements which results in the grain and microstructure refinement. Besides that, the strength bonding between different layers increases, which is attributed to the fine-grain strengthening and dispersion strengthening effect of NbC. Further, the strong Co-C covalent bonds in the NbC/Co interface and the Co-Co metallic bond in the internal coating might be why the NbC can serve as an obstacle and have a strong drag and pinning effect on the grain boundary according to the first principle calculations.

Electronic and optical properties of CuGaS2 nanowires: a study of first principle calculations

In this work we study the electronic and optical properties of fully relaxed CuGaS2 nanowires using the pseudo-potential density functional method. In our calculations we have investigated nanowires with two shapes of hexagonal and triangular with their corresponding diameters in the order of 8 to 15 A in (1–10) growth direction. For CuGaS2 bulk, the geometrical parameters such as anion displacement and equilibrium lattice constant agree well with other theoretical and experimental results. We have shown that for the CuGaS2 nanowires, there is an important contraction of the Cu-S and Ga-S bond lengths in the wires of 2.1% and 1.24% of the bulk value. In addition, in this manuscript the electronic properties such as band structures and atom-projected density of states have been examined. Our results show that while the nanowire diameter increases, the band gap decreases. From partial density of states we found that the greatest valence bands involve atoms which are placed at the surface. The optical constants, the dielectric function, reflectivity, refractive index and absorption of the nanowires have been analyzed. The results show that compared to the CuGaS2 bulk, the corresponding peaks of dielectric functions of CuGaS2 nanowires are blue-shifted. The calculations reveal that the dielectric functions of the nanowires augment while the nanowires’ size increases. It is also found that the peaks related to optical parameters of nanowires are affected by the diameter of the nanowire.

The hydrogen storage capacity of Sc atoms decorated porous boron fullerene B40: A DFT study

The hydrogen storage capacity of transition metal Sc atoms decorated porous boron fullerene B40 is investigated by the pseudopotential density functional method. The B40 cage contains two B6 cavities (diameter: 3.36 Å) and four B7 holes (diameter: 3.68 Å). It is calculated that the structures with the Sc atom outside the hollow sites of these cavities are the most stable. The calculated binding energy of the Sc atom to the B6 and B7 cavities on the surface of B40 are 4.61 and 5.24 eV, much larger than the experimental cohesive energy of bulk Sc (3.90 eV/atom). Moreover, the distance between the neighboring two Sc atoms (5.61 Å) is considerably larger than that of the Sc2 dimer (3.20 Å), therefore, the problem of Sc atoms aggregative to form the Scn cluster is expected to be overcome. The average adsorption energies and consecutive adsorption energies reveal that each Sc atom can most adsorb five H2 molecules. The calculated average hydrogen adsorption energies per H2 for B40(Sc–nH2)6 (n = 1–5) are in the energy range from 0.33 to 0.58 eV, which is suitable for hydrogen storage under near-ambient conditions. The Dewar–Kubas interaction dominates the adsorption of H2 by B40Sc6. The calculated desorption temperature and molecular dynamic simulation indicate that the B40(Sc–5H2)6 structure is easy to desorb H2 molecules. The HGD of the bulk [B40(Sc–5H2)4]4 is 6.18 wt%, a little smaller than that for B40(Sc–5H2)6 (8.3%), however still exceeding the 5.5 wt% at 2017 specified by the US department of energy (DOE). Therefore, the stable B40 structure decorated by the Sc atoms can be applied as one candidate for hydrogen storage materials under near-ambient conditions.

Adsorption of hydrogen in Scandium/Titanium decorated nitrogen doped carbon nanotube

Nitrogen doped Carbon Nanotube with divacancy (4ND-CNxNT) that is decorated with Scandium and Titanium as potential hydrogen storage medium using the pseudo potential density functional method was investigated. Highly localized states near the Fermi level, which are derived from the nitrogen defects, contribute to strong Sc and Ti bindings, which prevent metal aggregation and improve the material stability. A detailed Comparison of the Hydrogen adsorption capability with promising system-weight efficiency of Sc over Ti was elucidated when functionalized with 4ND-CNxNT. Finally, the (Sc/4ND)10-CNxCNT composite material has a thermodynamically favorable adsorption and consecutive adsorption energy for ideal reversible adsorption and desorption of hydrogen at room temperature such that it can hold at least 5.8 wt% hydrogen molecules at the LDA and GGA level.

Ab initio study of doping mechanisms in BaTiO3-BiYO3

A density functional plane-wave pseudopotential method is used to study the doping mechanisms of impurity defects(BiBa, YTi) in BaTiO3-BiYO3. Single BiBa and YTi impurities have little structure distortion. Bi forms ionic bond with nearby O atom in single Bi impurity, Y formed [YO6] octahedral in single Y impurity. However, in the co-doped BiBa and YTi structure, Bi formed three valence bonds with nearby O atom, which causes the large structure distortion. The doped ion makes the mobile of Ti4+ difficult and loss local ferroelectricity, which will broaden the dielectric constant temperature curve and increase the temperature stability of BaTiO3 ceramic matrix.

LaAlO3 as the heterogeneous nucleus of ferrite: Experimental investigation and theoretical calculation

The hardfacing (harden-surface-welding) metals without and with La2O3 were prepared. The microstructures of the hardfacing metals were observed by optical microscopy. The phase structures were determined by X-ray diffraction. The morphologies and compositions of the inclusions were observed by field emission scanning electron microscope equipped with energy dispersive X-ray spectrometry. The free energies of the La-inclusions which may exist in the hardfacing molten pool were calculated according to thermodynamic theory. Subsequently, the surface properties of LaAlO3(100), ferrite(100) and ferrite(110) surfaces, the interfacial properties of LaAlO3(100)/Ferrite(100) and LaAlO3(100)/Ferrite(110) interfaces, and the effectiveness of LaAlO3 as the heterogeneous nucleus of Ferrite were studied using a first-principles density functional plane-wave ultrasoft pseudopotential method. The experiment results indicate that, in the hardfacing metal, the ferrite grains can be refined and the numbers of the harmful inclusions can be reduced effectively by adding La2O3. Before the hardfacing molten pool solidification, La2O3 transforms into the LaAlO3 inclusion preferentially. The calculated results indicate that, in LaAlO3, most outer electrons of the Al atoms transfer to the O atoms, which means that the ionic bonds are formed between Al atoms and O atoms. Besides, because of the sp2 orbital hybridization, strong covalent bonds are formed between La atoms and O atoms with certain directionality. For LaAlO3(100) surface, there are two terminated structures, which are LaO terminated structure and AlO2 terminated one. When the La chemical potential is small, surface stability of AlO2 terminated structure is higher than that of LaO terminated one. While when the La chemical potential is large, LaO terminated structure is more stable than AlO2 terminated one. For the LaO terminated structure, the interfacial ideal adhesion work of the LaAlO3(100)/Ferrite(100) interface is larger than that of the LaAlO3(100)/Ferrite(110) interface while the interfacial energy of the LaAlO3(100)/Ferrite(100) interface is smaller than that of the LaAlO3(100)/Ferrite(110) interface, which indicates that the interfacial binding strength and interfacial stability of LaAlO3(100)/Ferrite(100) interface are both higher than those of the LaAlO3(100)/Ferrite(110) one. For the two LaAlO3/Ferrite interfaces, when the La chemical potential reaches −2.447 eV and −1.009 eV, their interfacial energies are both smaller than the liquid-solid interfacial energy of Ferrite(l)/Ferrite(s), which means that LaAlO3 can be the effective heterogeneous nucleus of Ferrite on current conditions.

Elastic and mechanical properties of Mg3Rh intermetallic compound: An ab initio study

In this work, density functional theory plane-wave pseudo potential method, with local density approximation (LDA) and generalized gradient approximation (GGA) are used to investigate the structural, elastic, mechanical and thermodynamic properties of the intermetallic compound Mg3Rh. Comparison of the calculated equilibrium lattice constants and experimental data shows very good agreement. The elastic constants were determined from a linear fit of the calculated stress-strain function according to Hooke's law. From the elastic constants, the bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio σ, anisotropy factor A, the ratio B/G and the hardness parameter H for Mg3Rh compound are obtained. Our calculated elastic constants indicate that the ground state structure of Mg3Rh is mechanically stable. The calculation results show that this intermetallic crystal is stiff, elastically anisotropic and ductile material. The sound velocities and Debye temperature are also predicted from elastic constants. This is the first quantitative theoretical prediction of these properties.