Electronic and magnetic properties of all 3d transition‐metal‐doped ZnO monolayers

Stable geometries, electronic structures, and magnetic properties of the ZnO monolayer doped with 3d transition‐metal (TM) (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) atoms substituting the cation Zn have been investigated using first‐principles pseudopotential plane wave method within density functional theory (DFT). It is found that these nine atomic species can be effectively doped in the ZnO monolayer with formation energies ranging from ?6.319 to ?0.132 eV. Furthermore, electronic structures and magnetic properties of ZnO monolayer can be modified by such doping. The results show that the doping of Cr, Mn, Fe, Co, Ni, and Cu atoms can induce magnetization, while no magnetism is observed when Sc, Ti, and V atoms are doped into the ZnO monolayer. The magnetic moment is mainly due to the strong p–d mixing of O and TM (Cr, Mn, Fe, Co, Ni, and Cu) orbitals. These results are potentially useful for spintronic applications and the development of magnetic nanostructures. © 2013 Wiley Periodicals, Inc.     

Structure,electronic, and magnetic properties of 3d transition metal intercalated borophene/BP heterostructures

The intercalation of various atoms or molecules has become one promising way to manipulate the electronic and magnetic properties of layered materials. Using density functional calculations, we explored the 3d transition metal (TM) intercalated α-borophene/black phosphorus (α-B/BP) heterostructure, TM@(α-B/BP) (TM = Sc-Ni), on their structure, electronic and magnetic properties. Our results demonstrate that TM@(α-B/BP)s can be ferromagnetic (FM), antiferromagnetic (AFM) and nonmagnetic depending on the choice of TM atoms, and most systems have large magnetic anisotropic energy. Particularly, Ti@(α-B/BP) is AFM semiconductor with Néel temperature of 470 K, which is much higher than room temperature. Moreover, the electronic and magnetic properties of TM@(α-B/BP)s can be further altered by the TM intercalation concentration. Our results provide a feasible way to design promising candidates for applications in electronic and information storage devices.     

Deformation of single‐walled carbon nanotubes by interaction with graphene: A first‐principles study

The interaction between single‐walled carbon nanotubes (SWNTs) and graphene were studied with first‐principles calculations. Both SWNTs and single‐layer graphene (SLG) or double‐layer graphene (DLG) display more remarkable deformations with the increase of SWNT diameter, which implies a stronger interaction between SWNTs and graphene. Besides, in DLG, deformation of the upper‐layer graphene is less than in SLG. Zigzag SWNTs show stronger interactions with SLG than armchair SWNTs, whereas the order is reversed for DLG, which can be interpreted by the mechanical properties of SWNTs and graphene. Density of states and band structures were also studied, and it was found that the interaction between a SWNT and graphene is not strong enough to bring about obvious influence on the electronic structures of SWNTs. © 2015 Wiley Periodicals, Inc.     

Structural and electronic properties of La‐doped CaTiO3 crystal

There is experimental and computational evidence that some important properties such as electrical conductivity and ferroelectricity in the CaTiO₃ crystal change according to the dopant states. Using an INDO quantum‐chemical computational method modified for crystal calculations we explore the stability of the La‐doped CaTiO₃ crystal in both phases, cubic and orthorhombic. The calculations are carried out by means of the supercell model based on the LUC (large unit cell) approach as it is implemented into the CLUSTERD computer code. The equilibrium geometry for impurity is found together with the crystalline lattice distortions. Atomic displacements and relaxation energies are analyzed in a comparative manner for the two crystallographic phases. A new effect of electron transfer from the local one‐electron energy level within the band‐gap to the conduction band is observed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Interface of ZnS single sheet and substrates: a first‐principles study

Two‐dimensional materials have aroused great interests because of their unique properties not seen in the bulk counterparts. The interface of the ZnS single sheet and substrates are studied in this paper. Different from isolated ZnS single sheet, here in this study, the ZnS single sheet has a remarkable corrugation feature because of the interaction between the ZnS single sheet and the substrate. The top‐site Zn means an attractive reaction with the substrate while the top‐site S means repulsive. For ZnS single sheet/Si(111) interface, the symmetry of the interface does not decrease after geometry optimization because the two layers have a good lattice matching. For ZnS single sheet/Ag(111) interface, an unbalanced interaction (attractive or repulsive) between the ZnS single sheet (Zn or S atom) and Ag surface leads to remarkable corrugation of the ZnS single sheet and the symmetry of the interface decreases. Copyright © 2017 John Wiley & Sons, Ltd.     

First‐principles study of metal/nitride polar interfaces: Ti/TiN

We have examined the optimal interface structure, ideal work of adhesion and bonding character of polar Ti(110)/TiN(111) interfaces by first‐principles density‐functional plane‐wave pseudopotential calculations. Both Ti‐ and N‐terminated interfaces, including six different interface structures, were calculated. The interface structure for each termination, continuing the TiN crystal structure across the interface, has the largest work of adhesion. Although both terminations yield substantial adhesion energies in the range 3–7 J m^?2, the N‐terminated interface is ～4 J m^?2 stronger than the Ti‐terminated interface. Analysis of the interfacial electronic structure shows that the Ti‐terminated interface is a mixed strong, metallic and weak covalent character, whereas the N‐terminated interface is a polar covalent bond similar to the Ti/TiC interface. Further study of the separation of the optimal interface shows that the cleavages will never fracture at the interface due to the strong bonding, which is consistent with the experimental results. Copyright © 2003 John Wiley & Sons, Ltd.     

The effects of oxygen co‐doping on structural,magnetic and optical properties of Mn‐doped GaN

The GaMnN and GaMnN: O films were obtained by annealing at different NH₃ flow rates. When the NH₃ flow rate was decreased to 20 sccm, the oxygen was co‐doped into GaMnN film and substituted the few host atoms, which were confirmed by the X‐ray Photoelectron Spectra. Moreover, the oxygen co‐doping in GaMnN film drastically enhanced the gain of the ferromagnetic (FM) state but oxygen as shallow donor in GaN offers little carriers. Hence, the enhanced FM state is not due to increase of carrier concentration. On optical properties, the oxygen co‐doping in GaMnN film will suppress the blue luminescence centered near 2.8 eV and make a blue shift of the photoluminescence spectra. Copyright © 2013 John Wiley & Sons, Ltd.     

Investigation on the electronic structures and nonlinear optical properties of alkali metal atom doped all‐cis 1,2,3,4,5,6‐hexafluorocyclohexane

On the basis of stable all‐cis 1,2,3,4,5,6‐hexafluorocyclohexane, a series of alkali metal atom doped M F₆C₆H₆ (M = Li, Na, and K) compounds were theoretically constructed and studied by using ab initio quantum chemistry method. The calculated results show that the HOMO–LUMO gap of the M F₆C₆H₆ conspicuously narrowed from 10.41 eV of pure F₆C₆H₆ to about 2.00 eV of M F₆C₆H₆. The electride characteristics of M F₆C₆H₆ are verified by their electronic structures, HOMOs, and small VIE values. As expected, these electrides possess considerable static first hyperpolarizabilities (β₀). Among the studied electrides, the largest β₀ of the Li F₆C₆H₆ is 7.00 × 10⁵ au, which is about 3030 times larger than pure F₆C₆H₆. TD‐M06‐2X calculations show that these larger β₀ values are attributed to lower transition energies for the crucial excited states of M F₆C₆H₆ systems. Further, the vibrational contributions to the static first hyperpolarizabilities of these molecules are also estimated. Moreover, Li atom doped dimer and trimer of F₆C₆H₆ also present unusual electride's features and exhibit dramatically large β₀. Thus, the F₆C₆H₆ interacting with the alkali metal atoms may be a potential promising NLO nanomaterial.     

Interactions between hydrogenated diamond surface and adsorbates with different concentration of NO2 molecules: A first‐principles study

To elucidate the effects of NO₂ and H₂O molecules on the surface conductivity of hydrogenated diamond film, models of various adsorbates containing different molecular ratio of NO₂ and H₂O on hydrogenated diamond (100) surfaces were constructed. The adsorption energies, equilibrium geometries of adsorbates, density of states, and atomic Mulliken populations were studied by using first‐principles method. The results showed that H₂O molecule in the adsorbate could weaken the interactions between the adsorbates and hydrogenated diamond surface significantly. Compared with H₂O molecule, NO₂ molecule relaxes more dramatically when adsorbed on hydrogenated diamond surface. In addition, density of states for C(100):H–2NO₂, C(100):H–NO₂, and C(100):H–NO₂ + H₂O systems are very similar to each other, which indicates an obvious peak at valence band maximum level for all the three samples. It can be attributed to mainly single occupied molecule orbital of NO₂ molecule and slightly C–H bond of C(100):H substrate. When the adsorbates contain one NO₂ and two H₂O molecules, the peak shifts slightly into valence band, but its intensity increases significantly. All the samples exhibit p‐type surface conductivity when adsorbed with pure NO₂ molecules, and the surface conductivity remains as H₂O molecules added into the NO₂ adsorbate layer. However, for oxygenated diamond surface, very week interactions generate between diamond surface and various adsorbates. All the oxygenated diamond (100) surfaces with various adsorbates containing different NO₂ and H₂O molecules on it exhibit an insulating property.     

H‐doped PbTiO3: Structure and electronic properties

The geometry and electronic properties of the interstitial H atom in the tetragonal PbTiO₃ crystal have been studied using an advanced quantum chemical computer code developed for the modeling of crystals. The inserted H atom was found to bind to one of the O atoms and to form the hydroxyl, O? H group, with the inter‐atomic distance equal to 0.93 Å and 1.00 Å for the hydroxyls containing O atom in the dimerized and nondimerized Ti? O? Ti chains, respectively. Atomic displacements in the vicinity of O? H complex are calculated and analyzed in relation to the H‐produced changes upon the atomic charges in defective region. The role of H impurity on the ferroelectric polarization in the tetragonal PbTiO₃ is discussed in terms of the results obtained in our research and those presented in the other studies on this subject. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Phase stability and mechanical properties of rhenium borides by first‐principles calculations

The phase stability and elastic properties of Re? B system were systematically investigated by use of the density functional theory. The formation enthalpies are negative for Re₃B, Re₇B₃, Re₂B, ReB, Re₂B₃, and ReB₂, indicating that they are thermodynamically stable. Re₇B₃, Re₂B, ReB, Re₂B₃, and ReB₂ are mechanically stable. Combining the study of enthalpy and pressure relationship with the convex hull, it was found that the ground state phases are Re₃B, Re₇B₃, and ReB₂ at zero pressure, in agreement with the experimental observations. At the pressure of 90 GPa, Re₃B, and ReB₂ are the most stable phases. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010     

Structural,mechanical, electronic,and thermodynamic properties of pure tungsten metal under different pressures: A first-principles study

The structural, mechanical, electronic, and thermodynamic properties of pure W metal under different pressures have been investigated using the first-principles method. Our calculated structural parameters are in good agreement with experimental and previous theoretical results. The obtained elastic constants show that pure W metal is mechanically stable. Elastic properties such as the bulk modulus (B), shear modulus (G), Young's modulus (E), Poisson's ratio (ν), Cauchy pressure (C′), and anisotropy coefficients (A) are calculated by the Voigt-Reuss-Hill method. The results show that the pressure can improve the strength of pure tungsten and has little effect on the ductility. In addition, the total density of states as a function of pressure is analyzed. Thermodynamic properties such as the Debye temperature, phonon dispersion spectrum, free energy, entropy, enthalpy, and heat capacity are also discussed.     

Chemical reaction dynamics of PeCB and TCDD decomposition: A tight‐binding quantum chemical molecular dynamics study with first‐principles parameterization

The decomposition reaction dynamics of 2,3,4,4′,5‐penta‐chlorinated biphenyl (2,3,4,4′,5‐PeCB), 3,3′,4,4′,5‐penta‐chlorinated biphenyl (3,3′,4,4′,5‐PeCB), and 2,3,7,8‐tetra‐chlorinated dibenzo‐p‐dioxin (2,3,7,8‐TCDD) was clarified for the first time at atomic and electronic levels, using our novel tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization. The calculation speed of our new method is over 5000 times faster than that of the conventional first‐principles molecular dynamics method. We confirmed that the structure, energy, and electronic states of the above molecules calculated by our new method are quantitatively consistent with those by first‐principles calculations. After the confirmation of our methodology, we investigated the decomposition reaction dynamics of the above molecules and the calculated dynamic behaviors indicate that the oxidation of the 2,3,4,4′,5‐PeCB, 3,3′,4,4′,5‐PeCB, and 2,3,7,8‐TCDD proceeds through an epoxide intermediate, which is in good agreement with the previous experimental reports and consistent with our static density functional theory calculations. These results proved that our new tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization is an effective tool to clarify the chemical reaction dynamics at reaction temperatures. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

First‐principles study of molecular hydrogen dissociation on doped Al12X (X = B,Al, C,Si, P,Mg, and Ca) clusters

Inspired by the concept of superatom via substitutionally doping an Al₁₃ magic cluster, we investigated the H₂ molecule dissociation on the doped icosahedral Al₁₂X (X = B, Al, C, Si, P, Mg, and Ca) clusters by means of density functional theory. The computed reaction energies and activation barriers show that the concept of superatom is still valid for the catalysis behavior of doped metal clusters. The hydrogen dissociation behavior on metal clusters characterized by the activation barrier and reaction energy can be tuned by controllable doping. Thus, doped Al₁₂X clusters might serve as highly efficient and low‐cost catalysts for hydrogen dissociation. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

First‐principles calculations of the stability and electronic properties of the PbTiO3 (110) polar surface

The structural and electronic properties of five terminations of cubic lead titanate (PbTiO₃) (110) polar surface were investigated by first‐principles total‐energy calculations using a periodic slab model. On the PbTiO termination, an anomalous filling of conduction band was observed, whereas on the O₂ termination, two surface oxygen atoms formed a peroxo group, demonstrating that the electronic structures of the two stoichiometric terminations undergo significant changes with respect to bulk materials. However, for the three nonstoichiometric TiO‐, Pb‐, and O‐terminated surfaces, their electronic structures are very similar to bulk. Charge redistribution results for the five terminations confirmed that electronic structure and surface composition changes are responsible for their polarity compensation. However, which mechanism actually dominates the stabilization process depends upon energetic considerations. A thermodynamic stability diagram suggested that the two stoichiometric terminations are unstable; however, the three nonstoichiometric terminations can be stabilized in some given regions. Furthermore, this study indicates that the very different stabilities and surface states filling behaviors of the PbTiO₃ (110) polar surface with respect to SrTiO₃ and BaTiO₃ ones seem to originate from the partially covalent characteristics of Pb O pairs. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009     

Insulator–metal transition driven by pressure and B‐site disorder in double perovskite La2CoMnO6

The ground state of double perovskite oxide La₂CoMnO₆ (LCMO) and how it is influenced by external pressure and antisite disorder are investigated systematically by first‐principles calculations. We find, on the consideration of both the electron correlation and spin–orbital coupling effect, that the LCMO takes on insulating nature, yet is transformed to half metallicity once the external pressure is introduced. Such tuning is accompanied by a spin‐state transition of Co²⁺ from the high‐spin state (te) to low‐spin state (te) because of the enhancement of crystal‐field splitting under pressure. Using mean‐field approximation theory, Curie temperature of LCMO with Co²⁺ being in low‐spin state is predicted to be higher than that in high‐spin state, which is attributed to the enhanced ferromagnetic double exchange interaction arising from the shrinkage of Co? O and Mn? O bonds as well as to the increase in bond angle of Co? O? Mn under pressure. We also find that antisite disorder in LCMO enables such transition from insulating to half‐metallic state as well, which is associated with the spin‐state transition of antisite Co from high to low state. It is proposed that the substitution of La³⁺ for the rare‐earth (RE) ions with smaller ionic radii could open up an avenue to induce a spin‐state transition of Co, rendering thereby the RE₂CoMnO₆ a promising half‐metallic material. © 2012 Wiley Periodicals, Inc.     

First-principles investigation of A-B intersite charge transfer and correlated electrical and magnetic properties in BiCu3Fe4O12

First-principles calculations using the augmented plane wave plus local orbitals method, as implemented in the WIEN2K code, have been carried out to study the A-B intersite charge transfer and the correlated electrical and magnetic properties of the perovskite BiCu(3)Fe(4)O(12), especially as regards the charge transfer. The results indicate that the charge transfer between A-site Cu and B-site Fe is by way of O 2p orbitals, and during this process orbital hybridization plays an important role. More importantly, the charge transfer is of 3d(9) + 4d(5)L(0.75) →3d(9)L + 4d(5) type (here L denotes an oxygen hole or a ligand hole). During this process, the magnetic interaction experiences a transition from Cu-Fe ferrimagnetic coupling to G-type antiferromagnetic coupling within B-site Fe with paramagnetic Cu(3+). As to electrical property, it undergoes a metal to insulator transition. All our calculated results are consistent with the available experimental results.     

Structural influence of transition metal (Sc,Y, and Lu) atoms inside gold nanoparticles

We theoretically investigated the influences of dopant transition metal atoms on structures and stability of gold nanoparticles. The optimized structures of Au₃M and Au₃M in an Au₃₂ cage (M = Au, Sc, Y, and Lu) obtained using relativistic density functional theory, show different configurations. Substitutions of one Au atom in the Au₄ cluster by only one M atom cause the Au₃M clusters to form equilateral triangles where M atoms prefer the central position, which is different from the original rhombus structure of a pure Au₄ cluster. All Au₃M nanoparticles, however, assume stable tetrahedral configurations in the Au₃₂ cage. Analysis of electronic structures indicates that the equilateral triangle Au₃M nanoparticles have higher chemical stability, in other words, lower reactivity than Au₃M@Au₃₂, while interaction energies between M and Au atoms in the Au₃M are smaller than those in Au₃M@Au₃₂. Different amounts of charge transfer and orbital hybridizations between the Au and M cause the change of the chemical stability and interaction energies. Our results indicate the potential manipulation of gold nanoparticle reactivity by metal substitution.