Ab Initio Electronic Calculations Research Articles

Ohmic contact in two-dimensional WS2/Hf2CX2 (X = F/OH) and WS2/graphene/Hf2C heterojunctions

Low-resistance Ohmic contacts are the key to improving the performance of electronic devices. By performing ab initio electronic calculations and quantum transport simulations, we systematically investigate the contact types of the original WS2/Hf2C, the functionalized WS2/Hf2CX2 (X = F/OH), and the graphene-doped WS2/graphene/Hf2C heterojunctions. The obtained results suggest that the strong interfacial coupling occurs in the WS2/Hf2C system, leading to the metallization of the WS2 layer. Functionalization of the Hf2C layer can significantly weaken the interlayer interactions. Thus, the semiconductor characteristics of the WS2 layer can be maintained in the WS2/Hf2CX2 (X = F/OH) and WS2/graphene/Hf2C heterojunctions. Stable Ohmic contacts are formed in these heterojunctions. The heights of the vertical electron Schottky barrier are −0.13 eV, −0.43 eV, and −0.12 eV for WS2/Hf2CF2, WS2/Hf2C(OH)2, and WS2/graphene/Hf2C, respectively. Based on these heterojunctions, we construct a two-probe field-effect transistor model and explore its quantum transport properties. In the lateral direction, all systems form n-type Schottky contacts. This investigation provides a basis for the selection of electrode materials based on WS2 devices.

Electron–phonon physics from first principles using the EPW code

EPW is an open-source software for ab initio calculations of electron–phonon interactions and related materials properties. The code combines density functional perturbation theory and maximally localized Wannier functions to efficiently compute electron–phonon coupling matrix elements, and to perform predictive calculations of temperature-dependent properties and phonon-assisted quantum processes in bulk solids and low-dimensional materials. Here, we report on significant developments in the code since 2016, namely: a transport module for the calculation of charge carrier mobility under electric and magnetic fields using the Boltzmann transport equation; a superconductivity module for calculations of phonon-mediated superconductors using the anisotropic multi-band Eliashberg theory; an optics module for calculations of phonon-assisted indirect transitions; a module for the calculation of small and large polarons without supercells; and a module for calculating band structure renormalization and temperature-dependent optical spectra using the special displacement method. For each capability, we outline the methodology and implementation and provide example calculations.

The influence of nitrogen proportion on the mechanical property of Fe–Ni alloy at extreme pressure

Proportions of doping elements is one of the important factors influencing the physical properties of the alloy. In this work, ab initio electronic calculations, applying density-functional theory, was used to investigate the mechanical properties of Fe–Ni–N alloys under the extreme pressure. Firstly, the stability of Fe11Ni3N2, Fe10Ni3N3, Fe9Ni3N4 and Fe8Ni3N5 alloys were estimated using binding energy and elastic constants. Fe11Ni3N2 and Fe9Ni3N4 were both stable basing on the Born criterion. Secondly, the density of Fe11Ni3N2 and Fe9Ni3N4 were smaller than that of Fe and closed to the one of preliminary reference earth model(PREM). The elastic properties of Fe11Ni3N2 and Fe9Ni3N4 which are stable were analyzed under pressure 130–360 GPa. The higher the proportion of N in ferroalloys, the larger elastic modulus and the faster the shear velocity (Vs).

Formula omitted]–[formula omitted] half-Heusler compounds as a potential class of three-dimensional Chern insulators

The high-Tc three-dimensional (3D) Chern insulators are in much demand for the future spin-polarized, massless and dissipationless current applications. Employing ab initio electronic calculations, a novel class of stoichiometric d0–d Dirac and parabolic half-metals in half-Heusler C1b structure with a good chance of application as quantum anomalous Hall materials is proposed including half-Heusler KMnP, KMnSb, RbMnP, RbMnSb, KMnN, and RbMnN. The robust Γ1–Γ5 band inversion across the Fermi level in the semi-metallic spin channel, which results from the s–d hybridization of Mn states together with the maximum d-shell exchange splitting, gives rise to a non-trivial topology with a Chern number C=1 in all the above compounds. With the intrinsic spin–orbit coupling included, a small gap appears in the semi-metallic spin channel that can be further magnified via uniaxial strain, thus converting the above compounds to genuine 3D Chern insulators. The above theoretical findings in d0–d half-Heusler structures together with the characteristic high Curie temperatures and dynamical stability, open an intriguing pathway to realization of quantum anomalous Hall effect in stoichiometric 3D materials.

On the Synthesis of the Astronomically Elusive 1-Ethynyl-3-Silacyclopropenylidene (c-SiC4H2) Molecule in Circumstellar Envelopes of Carbon-rich Asymptotic Giant Branch Stars and Its Potential Role in the Formation of the Silicon Tetracarbide Chain (SiC4)

Abstract Organosilicon molecules such as silicon carbide (SiC), silicon dicarbide (c-SiC2), silicon tricarbide (c-SiC3), and silicon tetracarbide (SiC4) represent basic molecular building blocks connected to the growth of silicon-carbide dust grains in the outflow of circumstellar envelopes of carbon-rich asymptotic giant branch (AGB) stars. Yet, the fundamental mechanisms of the formation of silicon carbides and of the early processes that initiate the coupling of silicon–carbon bonds in circumstellar envelopes have remained obscure. Here, we reveal in a crossed molecular beam experiment contemplated with ab initio electronic calculations that the astronomically elusive 1-ethynyl-3-silacyclopropenylidene molecule (c-SiC4H2, Cs, X1A′) can be synthesized via a single-collision event through the barrierless reaction of the silylidyne radical (SiH) with diacetylene (C4H2). This system represents a benchmark of a previously overlooked class of reactions, in which the silicon–carbon bond coupling can be initiated by a barrierless and overall exoergic reaction between the simplest silicon-bearing radical (silylidyne) and a highly hydrogen-deficient hydrocarbon (diacetylene) in the inner circumstellar envelopes of evolved carbon-rich stars such as IRC+10216. Considering that organosilicon molecules like 1-ethynyl-3-silacyclopropenylidene might be ultimately photolyzed to bare carbon–silicon clusters like the linear silicon tetracarbide (SiC4), hydrogenated silicon–carbon clusters might represent the missing link eventually connecting simple molecular precursors such as silane (SiH4) to the population of silicon-carbide based interstellar grains ejected from carbon-rich AGB stars into the interstellar medium.

Tunable photoelectronic properties of hydrogenated-silicene/halogenated-silicene superlattices for water splitting

We propose a novel two-dimensional (2D) lateral superlattice based on silicene alternately saturated by hydrogen and halogen atoms, named as hydrogenated-silicene/halogenated-silicene superlattices (SHSXSLs, X = F, Cl, Br, and I). Employing ab initio electronic calculations, we systematically investigate the structural, electronic, and optical properties of SHSXSLs. Our results show that these superlattices are much stable than silicene as saturating the dangling bonds and the bandgap and carrier effective mass of superlattices can be modulated by the width of components due to the confinement and interfacial effects. By calculating the band alignment, it is found that all superlattices exhibit the type I alignment. Specifically, SHSCl,BrSLs have very small valence band offset and large conduction band offset, which can separate electrons and holes in these systems. Furthermore, the band edge positions of SHSCl,BrSLs satisfy the redox potential of the water splitting and SHSCl,BrSLs exhibit strong absorption in the visible region, suggesting that these superlattices are promising materials for photovoltaics and photocatalytics. This new type of superlattice structure can be applied to other 2D materials with strong activity to enhance the stability and modulate the properties effectively.

A thorough theoretical mechanistic study of OH-initiated oxidative degradation mechanism for large polycyclic aromatic hydrocarbons

To get a better understanding of oxidative degradation of polycyclic aromatic hydrocarbons (PAH) in the atmospheric and combustion chemistry, benzo[ghi]perylene (BP) was selected as their prototype to be investigated by combining ab initio electronic structure theory calculations (M06-2X/6-31G(d,p)) and the conventional transition state theory. For BP-OH adducts, O2 addition favored the armchair edge comparing with the free and zigzag ones. The overall rate constant was increased due to the presence of armchair site; and thereby it has a prompt effect on the oxidation reactivity. This implies that given an arbitrary shaped PAH, OH attack preferentially occurs at the free-edge sites and subsequent O2 attack favors the armchair-edge sites. Morever, the current study provides new kinetics and thermodynamics data for OH-initiated oxidative degradation mechanism of benzo[ghi]perylene in a wider temperature range, which can be used for modeling the fate of large PAHs during combustion and in the atmosphere.

Alternative Approach for the Determination of Mean Free Paths of Electron Scattering in Liquid Water Based on Experimental Data.

Mean free paths of low-energy electrons in liquid water are of importance for modeling many physicochemical processes, but neither theoretical predictions nor experimental results have converged for these parameters. We therefore introduce an approach to determine elastic and inelastic mean free paths (EMFP, IMFP) based on experimental data. We show that ab initio calculations of electron scattering with water clusters converge with cluster size, thus providing access to condensed-phase scattering. The results are used in Monte Carlo simulations to extract EMFP and IMFP from recent liquid-microjet experiments that determined the effective attenuation length (EAL) and the photoelectron angular distribution (PAD) following oxygen 1s-ionization of liquid water. For electron kinetic energies from 10 to 300 eV, we find that the IMFP is noticeably larger than the EAL. The EMFP is longer than that of gas-phase water and the IMFP is longer compared to latest theoretical estimations, but both EMFP and IMFP are much shorter than suggested by experimental measurements of integral cross sections for amorphous ice.

Projector augmented-wave method: an analysis in a one-dimensional setting

In this article, a numerical analysis of the projector augmented-wave (PAW) method is presented, restricted to the case of dimension one with Dirac potentials modeling the nuclei in a periodic setting. The PAW method is widely used in electronic ab initio calculations, in conjunction with pseudopotentials. It consists in replacing the original electronic Hamiltonian H by a pseudo-Hamiltonian HPAW via the PAW transformation acting in balls around each nuclei. Formally, the new eigenvalue problem has the same eigenvalues as H and smoother eigenfunctions. In practice, the pseudo-Hamiltonian HPAW has to be truncated, introducing an error that is rarely analyzed. In this paper, error estimates on the lowest PAW eigenvalue are proved for the one-dimensional periodic Schrödinger operator with double Dirac potentials.

Interfacial charge transfers and interactions drive rectifying and negative differential resistance behaviors in InAs/graphene van der Waals heterostructure

Vertical heterostructures of two-dimensional (2D) materials are excellent candidates for designing next-generation electronic devices with superior performance. By using both ab initio electronic calculations and quantum transport simulations, we investigated the electronic and transport properties of InAs/graphene heterostructure. The results reveal that electrons and holes accumulate at different layers after the adsorption of InAs layer, forming the built-in electronic field at the interface. The electrostatic potential energy of InAs layer is higher than that of graphene, and it favors more electrons transferring from InAs to graphene layer. Comparing the comment methods by introducing impurity and carriers' injection, rectifying and negative differential resistance behaviors can also be realized by the combined effects of electron-hole distribution, interfacial hybridization, and contact barrier in InAs/graphene heterostructure device. It shows that the rectifying ration gradually increases with bias voltage, and the negative differential resistance effect happens at either positive or at negative bias voltage regions. Electrostatic potential distribution and contact barrier play important roles in determining transport properties. Increasing interfacial hybridization is helpful for transmission enhancement in the weak interlayer interaction van der Waals heterostructure.

Tuning Schottky barriers for monolayer GaSe FETs by exploiting a weak Fermi level pinning effect.

Monolayer gallium selenide (GaSe), an emerging two-dimensional semiconductor, holds great promise for electronics and optoelectronics. In reality, the contact properties between a semiconductor and the electrodes play a vital role in device performance. Thus, selecting suitable electrode materials with zero contact resistance is critical and challenging. Here, we explore the contact properties and electronic transport of monolayer GaSe with a series of electrode materials (including transition metals and MXenes) by ab initio electronic calculations and quantum transport simulations. Bare MXenes (V2C, Mo2C, Nb2C) and transition metals (Ni, Cu, Pt, Au) form strong chemical bonds with monolayer GaSe and lead to n-type contacts with Schottky barriers of 0-0.53 eV. The O-terminated MXenes (V2CO2 and Nb2CO2) establish van der Waals interactions with the GaSe sheet and form p-type contacts with vanishing hole Schottky barriers but large tunneling barriers. Impressively, Ohmic contact is achieved by the V2C and Mo2C electrodes, which is further demonstrated by the linear I-V curves. These contact systems exhibit a weak Fermi level pinning effect, with Schottky barriers in both the vertical and lateral directions controllable by the work function of the electrodes. To promote the carrier injection process, we propose to select electrode materials with a strong surface polarization and low work function (<5.0 eV) for GaSe-based devices.

Atomic-scale characterization of the interfacial phonon in graphene/SiC

Epitaxial graphene on SiC that provides wafer-scale and high-quality graphene sheets on an insulating substrate is a promising material to realize graphene-based nanodevices. The presence of the insulating substrate changes the physical properties of free-standing graphene through the interfacial phonon, e.g., limiting the mobility. Despite such known impacts on the material properties, a complete and microscopic picture is missing. Here, we report on atomically resolved inelastic electron tunneling spectroscopy (IETS) with a scanning tunneling microscope for epitaxial graphene grown on $4H$-SiC(0001). Our data reveal a strong spatial dependence in the IETS spectrum, which cannot be explained by intrinsic graphene properties. We show that this variation in the IETS spectrum originates from a localized low-energy vibration of the interfacial Si atom with a dangling bond via ab initio electronic and phononic state calculations. This insight may help advancing graphene device performance through interfacial control.

Electrical Contacts in Monolayer Arsenene Devices.

Arsenene, arsenic analogue of graphene, as an emerging member of two-dimensional semiconductors (2DSCs), is quite promising in next-generation electronic and optoelectronic applications. The metal electrical contacts play a vital role in the charge transport and photoresponse processes of nanoscale 2DSC devices and even can mask the intrinsic properties of 2DSCs. Here, we present a first comprehensive study of the electrical contact properties of monolayer (ML) arsenene with different electrodes by using ab initio electronic calculations and quantum transport simulations. Schottky barrier is always formed with bulk metal contacts owing to the Fermi level pinning (pinning factor S = 0.33), with electron Schottky barrier height (SBH) of 0.12, 0.21, 0.25, 0.35, and 0.50 eV for Sc, Ti, Ag, Cu, and Au contacts and hole SBH of 0.75 and 0.78 eV for Pd and Pt contacts, respectively. However, by contact with 2D graphene, the Fermi level pinning effect can be reduced due to the suppression of metal-induced gap states. Remarkably, a barrier free hole injection is realized in ML arsenene device with graphene-Pt hybrid electrode, suggestive of a high device performance in such a ML arsenene device. Our study provides a theoretical foundation for the selection of favorable electrodes in future ML arsenene devices.

AIMS simulation study of ultrafast electronically nonadiabatic chemistry of methyl azide and UV–VIS spectroscopic study of azido-based energetic plasticizer bis(1,3-diazido prop-2-yl)malonate

To gain insight into the ultrafast electronically nonadiabatic chemistry of azido-based energetic plasticizer, we have explored the nonadiabatic chemical dynamics of an azido-based model analog molecule, methyl azide (MAz), using ab initio multiple spawning (AIMS) simulation and electronic structure theory calculations. Molecular nitrogen (N2) is predicted to be the initial product of MAz following its electronic excitation to the S1 electronically excited state. AIMS-based simulation reveals that electronically excited azido-based molecules undergo extremely fast (approximately in 40 femtoseconds) relaxation to the ground state via the (S1/S0)CI conical intersection. Furthermore, this relaxation process involves the NN bond elongation along with the bending of N3 moiety. This is the first report on the electronically non-adiabatic chemical dynamics (in ultrafast time domain) of methyl azide. Finally, using ultraviolet–visible (UV–VIS) spectroscopy, we comment on the electronically nonadiabatic chemistry of azido-based energetic plasticizer, bis(1,3-diazido prop-2-yl)malonate.

Schottky Barriers in Bilayer Phosphorene Transistors.

It is unreliable to evaluate the Schottky barrier height (SBH) in monolayer (ML) 2D material field effect transistors (FETs) with strongly interacted electrode from the work function approximation (WFA) because of existence of the Fermi-level pinning. Here, we report the first systematical study of bilayer (BL) phosphorene FETs in contact with a series of metals with a wide work function range (Al, Ag, Cu, Au, Cr, Ti, Ni, and Pd) by using both ab initio electronic band calculations and quantum transport simulation (QTS). Different from only one type of Schottky barrier (SB) identified in the ML phosphorene FETs, two types of SBs are identified in BL phosphorene FETs: the vertical SB between the metallized and the intact phosphorene layer, whose height is determined from the energy band analysis (EBA); the lateral SB between the metallized and the channel BL phosphorene, whose height is determined from the QTS. The vertical SBHs show a better consistency with the lateral SBHs of the ML phosphorene FETs from the QTS compared than that of the popular WFA. Therefore, we develop a better and more general method than the WFA to estimate the lateral SBHs of ML semiconductor transistors with strongly interacted electrodes based on the EBA for its BL counterpart. In terms of the QTS, n-type lateral Schottky contacts are formed between BL phosphorene and Cr, Al, and Cu electrodes with electron SBH of 0.27, 0.31, and 0.32 eV, respectively, while p-type lateral Schottky contacts are formed between BL phosphorene and Pd, Ti, Ni, Ag, and Au electrodes with hole SBH of 0.11, 0.18, 0.19, 0.20, and 0.21 eV, respectively. The theoretical polarity and SBHs are in good agreement with available experiments. Our study provides an insight into the BL phosphorene-metal interfaces that are crucial for designing the BL phosphorene device.

Effects of Interlayer Coupling on Hot‐Carrier Dynamics in Graphene‐Derived van der Waals Heterostructures

Graphene exhibits promise as a plasmonic material with high mode confinement that could enable efficient hot carrier extraction. The lifetimes and mean free paths of energetic carriers have been investigated in free‐standing graphene, graphite, and a heterostructure consisting of alternating graphene and hexagonal boron nitride layers using ab initio calculations of electron–electron and electron–phonon scattering in these materials. It is found that the extremely high lifetimes (3 ps) of low‐energy carriers near the Dirac point in graphene, which are a 100 times larger than that in noble metals, are reduced by an order of magnitude due to interlayer coupling in graphite, but enhanced in the heterostructure due to phonon mode clamping. However, these lifetimes drop precipitously with increasing carrier energy and are smaller than those in noble metals at energies exceeding 0.5 eV. By analyzing the contribution of different scattering mechanisms and interlayer interactions, desirable spacer layer characteristics—high dielectric constant and heavy atoms—that could pave the way for plasmonic heterostructures with improved hot carrier transport have been identified.

Understanding the thermoelectric properties of LaCoO3 compound

We present the thermoelectric (TE) properties of LaCoO compound in the temperature range 300–600 K. The experimental value of Seebeck coefficient () at 300 K is found to be V/K. The value of decreases continuously with increase in temperature and reaches to V/K at K. The electronic and TE properties of the compound have also been investigated by combining the ab initio electronic structures and Boltzmann transport calculations. LSDA plus Hubbard U ( eV) calculation on low spin configuration of the compound gives an energy gap of eV, which is close to the experimentally reported energy gap. The effective mass of holes () at point is nearly two times larger than the value of effective mass of electrons () at FB point along the L and T directions, whereas the at FB point along the direction is nearly eight times larger than the value of at point along the FB direction. The large effective mass at FB point along the direction suggests that the TE property of this compound is mainly decided by the effective mass of the charge carriers in this direction. The calculated temperature dependent values of are in fairly good agreement with experimental data in the temperature range 300–360 K, and above this temperature slight deviation is observed. The value of power factor (PF) for n-type is times larger the value of p-type doped compound at 1100 K. The value of figure-of-merit (ZT) for n-type doped compound is obtained 0.35 in the temperature range 600–1100 K, which suggests that with appropriate n-type doping this compound can be used as a good TE material in the high temperature region.

Oxygen Generation from 18oxygen-Doped Li2CuO2 Caused By Electrochemical Oxidation

INTORDUCTION Li-ion batteries with high energy density have been required for power sources of electric vehicles. In particularly, it is crucial that the positive electrodes exhibit a large specific capacity with high cell voltage. The practical candidates for the electrode are limited such as Li2MnO3-based solid solutions. Based on our previous investigations on LiNi0.5Mn0.5O2, we have focused on Li2CuO2 and Li2CuO2-Li2NiO2 solid solutions [1, 2, 3]. They have some unique advantages which are different from other popular positive electrodes. Firstly, copper has abundant resources and less toxicity compared to cobalt or nickel. Secondary, they expect to exhibit a high-capacity due to a large amount of Li like as Li2MnO3. Furthermore, they adopt mutually similar structure which has the square planner CuO4 with the copper atom in the center and the oxygen atoms at the corners. Thus, these structures lead to characteristics of electronic structure that Cu 3d and O2p orbitals overlap dominantly over a wide range of energy level. Hence, both copper and oxygen electrons in the Cu-containing oxides may participate in the electrochemical oxidizing and reducing reactions. Our ab-initio electronic calculation strongly suppports that electrons by electrochemical oxidation may be removed considerably from both copper and then oxygen atoms [1]. In addition, XRD patterns using synchrotron radiation showed the formation of CuO after the first charging [1, 2]. By combining our experimental and calculated results, oxygen could participate in charging process of Li2CuO2 and Li2CuO2-Li2NiO2solid solutions. The objective of this paper is to detect O2 release directly from 18O isotope-doped Li2CuO2 by use of GC-MS analysis, and then to discuss the role of the oxygen on the electrochemical mechanism of Li2CuO2 and Li2CuO2-Li2NiO2solid solutions. Experimental The samples for x = 0-0.4 in Li2Cu1-x Ni x O2 were prepared by a combination of co-precipitation and solid state reaction. The co-precipitates were obtained from Cu(CH3COO)2∙H2O and Ni(CH3COO)2∙4H2O by dropping 1 M LiOH solution. After heating dried co-precipitates at 873 K for 6 h in air, Cu and Ni oxides were obtained. They were mixed with chemical grade Li2O and sintered at 1073 K for 24 h under N2 flow. A sample for 18O isotope - doped was prepared by filling and sealing with 18O2 gas. Electrochemical testing was carried out by coin-type cells with Li/1M LiPF6 in EC:DMC(1:1)/samples at 298 K. The positive electrode was composed of the following materials; specimen: acetylene black: PTFE = 30:15:1.5 (wt.%). The rate of constant current was 1/20 C in the range of 2.0-4.3 V. The in-situelectrochemical testing cell was connected with GC-MS (Gas Chromatography Mass Spectrometry) analysis equipment and the measurement was performed with on-line to detect oxygen generation directly during charging process. RESULTS AND DISCUSSIONS All the obtained samples for 18O isotope-doped Li2CuO2 and x = 0-0.4 in Li2Cu1-x Ni x O2 showed an orthorhombic single phase and formed a Li2CuO2-Li2NiO2 solid solution. Fig.1(a) shows a charge curve of 18O-doped Li2CuO2 and GC-MS spectra collected at m/z = 35.90-36.40 is shown in Fig.1(b). The results of electrochemical testing were good agreement with those of our reported earlier [3]. A remarkable increasing of the detected intensity was observed from 4.1 to 4.3 V and then after the completion of the electrochemical testing the intensity decreased. Whereas, the intensity corresponding to the mass number of 36 was not detected for Li2CuO2 prepared by conventional oxygen gas. These results shows direct O2 gas generation clearly from Li2CuO2 by its electrochemical oxidation. On the other hands, the charge and discharge specific capacities increased with the amount of Ni contents. A reversible capacity of about 300 mAhg-1 for x = 0.3 in Li2Cu1-x Ni x O2 was obtained and the capacity was maintained after 10 cycles. Based on these results, we will discuss the role of the oxygen on the electrochemical mechanism of Li2CuO2 and Li2CuO2-Li2NiO2solid solutions. REFERENCES 1. Y. Arachi et al., J. Power Sources, 196, (2011) 6939. 2. Y. Arachi et al., Solid State Ionics, 225, (2012) 611. 3. Y. Arachi et al., ECS Trans, 50(2013)143. Figure 1

Lattice Dynamics Study of Phonon Instability and Thermal Properties of Type-I Clathrate K₈Si46 under High Pressure.

For a further understanding of the phase transitions mechanism in type-I silicon clathrates K8Si46, ab initio self-consistent electronic calculations combined with linear-response method have been performed to investigate the vibrational properties of alkali metal K atoms encapsulated type-I silicon-clathrate under pressure within the framework of density functional perturbation theory. Our lattice dynamics simulation results showed that the pressure induced phase transition of K8Si46 was believed to be driven by the phonon instability of the calthrate lattice. Analysis of the evolution of the partial phonon density of state with pressure, a legible dynamic picture for both guest K atoms and host lattice, was given. In addition, based on phonon calculations and combined with quasi-harmonic approximation, the specific heat of K8Si46 was derived, which agreed very well with experimental results. Also, other important thermal properties including the thermal expansion coefficients and Grüneisen parameters of K8Si46 under different temperature and pressure were also predicted.

Polar Spinel-Perovskite Interfaces: an atomistic study of Fe3O4(111)/SrTiO3(111) structure and functionality.

Atomic resolution scanning transmission electron microscopy and electron energy loss spectroscopy combined with ab initio electronic calculations are used to determine the structure and properties of the Fe3O4(111)/SrTiO3(111) polar interface. The interfacial structure and chemical composition are shown to be atomically sharp and of an octahedral Fe/SrO3 nature. Band alignment across the interface pins the Fermi level in the vicinity of the conduction band of SrTiO3. Density functional theory calculations demonstrate very high spin-polarization of Fe3O4 in the interface vicinity which suggests that this system may be an excellent candidate for spintronic applications.