By solving the Eliashberg equations for the gap function, the superconducting transition temperature of a proposed low-temperature liquid state of metallic hydrogen is found to be comparable to that obtained, with similar approximations,... more
By solving the Eliashberg equations for the gap function, the superconducting transition temperature of a proposed low-temperature liquid state of metallic hydrogen is found to be comparable to that obtained, with similar approximations, for the solid. This indicates that metallic hydrogen may be a superconducting liquid in the density range 1.6>=rs>=1.3, where the melting point is expected to be fairly low.
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Cobalt-doped titanium dioxide, or CTO, has emerged in the past few years as a semiconducting, transparent, room-temperature ferromagnet. Very recently it has been shown that the magnetism in anatase-structure CTO often originates in... more
Cobalt-doped titanium dioxide, or CTO, has emerged in the past few years as a semiconducting, transparent, room-temperature ferromagnet. Very recently it has been shown that the magnetism in anatase-structure CTO often originates in surface nanoparticles or ...
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Periodic Hartree-Fock total-energy calculations on two-dimensional slabs have been used to study the symmetry-conserving relaxation of the nonpolar (101¯0) surface of ZnO. We find that it is energetically favorable for the Zn-O surface... more
Periodic Hartree-Fock total-energy calculations on two-dimensional slabs have been used to study the symmetry-conserving relaxation of the nonpolar (101¯0) surface of ZnO. We find that it is energetically favorable for the Zn-O surface dimers to tilt slightly (by 2.3 °) and move downwards towards the slab, and for the dimer bond to shorten significantly. Our results agree fairly well with those of a recent density-functional calculation, but disagree with empirical tight-binding theory which predicts surface bonds to shorten only slightly while the surface dimers undergo a large tilt (18 °). The available experimental data lies between the ab initio and tight-binding results with large error bars. We have tested the effects of several refinements of our Hartree-Fock calculation, including improvements of the orbital basis set and precision tolerances, the use of thicker slabs in approximating the semi-infinite crystal, and post-self-consistent-field density-functional correlation corrections to the total energy. None of these refinements significantly changed our results. We discuss possible reasons for the disagreement between our results and those of tight-binding theory.
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Low-temperature polymorphs of ZrO 2 and HfO 2 : A density-functional theory study. John E. Jaffe 1 , Rafał A. Bachorz 1 , and Maciej Gutowski 1,2 * 1 Chemical Sciences Division, Fundamental Sciences Directorate, Pacific Northwest ...
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Gaussian basis density functional theory for systems periodic in two or three dimensions: Energy and forces. [The Journal of Chemical Physics 105, 10983 (1996)]. John E. Jaffe, Anthony C. Hess. Abstract. We describe a formulation ...
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Ab initio study of a CO monolayer adsorbed on the (1010) surface of ZnO. [The Journal of Chemical Physics 104, 3348 (1996)]. John E. Jaffe, Anthony C. Hess. Abstract. Periodic HartreeFock total energy calculations on two‐dimensionally ...
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The Energy Citations Database (ECD) provides access to historical and current research (1948 to the present) from the Department of Energy (DOE) and predecessor agencies.
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The Energy Citations Database (ECD) provides access to historical and current research (1948 to the present) from the Department of Energy (DOE) and predecessor agencies.
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The Energy Citations Database (ECD) provides access to historical and current research (1948 to the present) from the Department of Energy (DOE) and predecessor agencies.
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Using a first-principles all-electron band-structure approach, we show that the anomalous (> 50%) reduction in the band gaps of the AIBIIICVI2 chalcopyrite semiconductors relative to their II-VI isoelectronic analogs results both from a... more
Using a first-principles all-electron band-structure approach, we show that the anomalous (> 50%) reduction in the band gaps of the AIBIIICVI2 chalcopyrite semiconductors relative to their II-VI isoelectronic analogs results both from a pure structural effect (the anion displacements reflecting the mismatch of classical elemental radii) and from a purely electronic effect (p-d repulsion in the valence band), with a small coupling between the two factors.
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We have investigated the mobility of isolated native point defects in CdTe by first-principles calculations. Cd vacancies and interstitials, Te interstitials and Te-on-Cd antisites were considered. Diffusion barriers were found by the NEB... more
We have investigated the mobility of isolated native point defects in CdTe by first-principles calculations. Cd vacancies and interstitials, Te interstitials and Te-on-Cd antisites were considered. Diffusion barriers were found by the NEB (nudged- elastic-band) technique within the PAW-LDA method as implemented in the VASP code. Diffusion constants are estimated, and some implications for the growth of radiation detector material are suggested, especially in regard to the formation of Te precipitates. Comparisons to experimental and earlier theoretical studies are also provided.
Cobalt-doped titanium dioxide, or CTO, has emerged in the past few years as a semiconducting, transparent, room-temperature ferromagnet. Very recently it has been shown that the magnetism in anatase-structure CTO often originates in... more
Cobalt-doped titanium dioxide, or CTO, has emerged in the past few years as a semiconducting, transparent, room-temperature ferromagnet. Very recently it has been shown that the magnetism in anatase-structure CTO often originates in surface nanoparticles or Co-rich regions that have a much-enhanced substitutional Co content up to 40% of Ti sites, so that magnetic CTO is not a true dilute magnetic semiconductor (DMS), but rather a fairly high-density spin system. In this work we describe a computational study of Co-rich CTO using the Generalized Gradient Approximation (GGA) to density functional theory (DFT) within the supercell model. Our total energy calculations show a strong tendency for Co-atom clustering or segregation on Ti sites. There is also a strong tendency for the oxygen vacancies to form complexes with the Co atoms. In addition, we find that the oxygen stoichiometry plays an essential role in determining the system's magnetic order. The largest ordered moments require at least enough oxygen vacancies to put all of the Co atoms in the +2 charge state, as they indeed appear to be experimentally, so that the conventional DMS mechanism could only apply via n-type carriers. We find a small but not negligible spin density associated with Ti atoms near the vacancy sites, suggesting an F-center-mediated interaction between the much larger Co moments.
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Native point defects in reduced TiO2, namely the oxygen vacancy and Ti interstitial, were investigated computationally for both the rutile and anatase structures. The generalized gradient approximation to density functional theory was... more
Native point defects in reduced TiO2, namely the oxygen vacancy and Ti interstitial, were investigated computationally for both the rutile and anatase structures. The generalized gradient approximation to density functional theory was used along with a plane-wave expansion and ultrasoft pseudopotentials. Defect formation energies were calculated after geometry relaxation from O vacancies created in the bulk rutile and anatase lattices, from the experimental Ti interstitial position in rutile, and from several trial initial geometries for the Ti interstitial in anatase. Contrary to traditional assumptions but consistent with much recent evidence, the Ti interstitial was found to be predominant over the O vacancy in rutile under most conditions. Donor ionization energies in rutile were consistent with experiment. Surprisingly, the calculations also indicate a dominant role for the Ti interstitial in anatase (lower formation energy than the O vacancy, though not by as much as in rutile, and much shallower ionization levels.) We evaluate these findings against experimental data on pure n-type TiO2, and discuss possible implications for transition metal cation doping as well as anion doping of TiO2.
We have used high-energy resolution X-ray photoelectron spectroscopy to measure valence band offsets at the epitaxial anatase TiO 2(0 0 1)/ n-SrTiO 3(0 0 1) heterojunction prepared by molecular beam epitaxy. The valence band offsets range... more
We have used high-energy resolution X-ray photoelectron spectroscopy to measure valence band offsets at the epitaxial anatase TiO 2(0 0 1)/ n-SrTiO 3(0 0 1) heterojunction prepared by molecular beam epitaxy. The valence band offsets range between -0.06 ± 0.05 and +0.16 ± 0.05 eV for anatase thicknesses between 1 and 8 monolayers and three different methods of substrate surface preparation, with no systematic dependence on film thickness. The conduction band offset (CBO) varies over a comparable range by virtue of the fact that anatase and SrTiO 3 exhibit the same bandgap (˜3.2 eV). In contrast, density functional theory predicts the VBO to be +0.55 eV. The lack of agreement between theory and experiment suggests that either some unknown factor in the interface structure or composition excluded from the modeling is influencing the band offset, or that density functional theory cannot accurately calculate band offsets in these oxide materials. The small experimental band offsets have important implications for the use of this interface for fundamental investigations of surface photocatalysis. Neither electrons nor holes are likely to become trapped in the substrate and thus be unable to participate in surface photocatalytic processes.
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In contrast to zinc-blende semiconductors, where the nonpolar (110) surface has the lowest energy, our first-principles calculations on the chalcopyrite semiconductor CuInSe2 reveal that facets terminated by the (112)-cation and... more
In contrast to zinc-blende semiconductors, where the nonpolar (110) surface has the lowest energy, our first-principles calculations on the chalcopyrite semiconductor CuInSe2 reveal that facets terminated by the (112)-cation and (1̄1̄2̄)-Se polar surfaces are lower in energy than the unfaceted (110) plane, despite the resulting increased surface area. This explains the hitherto puzzling existence of polar microfacets on nominally nonpolar (110) chalcopyrite surfaces. The extraordinary stability of these polar facets originates from the effective neutralization of surface charge by low-energy ordered CuIn antisite or Cu vacancy surface defects, while the relaxed but defect-free (112) surface is metallic and much higher in energy. We explain the low carrier density of the observed faceted surface in terms of autocompensation between opposite-polarity facets.
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TiO2 in both the rutile and anatase structures has been proposed as an absorber of sunlight for photocatalytic processes, including water splitting to produce hydrogen from solar energy. However, the large band gap of TiO2, about 3.0 eV,... more
TiO2 in both the rutile and anatase structures has been proposed as an absorber of sunlight for photocatalytic processes, including water splitting to produce hydrogen from solar energy. However, the large band gap of TiO2, about 3.0 eV, permits the use of only a small part of the solar spectrum. Alloying with other elements, and especially anion doping with nitrogen, sulfur or other anions in place of oxygen, has shown promise for reducing the band gap of the material, permitting more of the solar spectrum to be used so that photocatalysis with TiO2 can be made more efficient. However, little is known about the concentration dependence of the bandgap reduction, or about autocompensation of nonisovalent dopants by native defects such as the oxygen vacancy. We have calculated defect formation energies and changes in the DFT bandgap for rutile TiNxO2-x for x = 0.042, 0.083, 0.167 and 0.25. The band gap initially decreases with increasing x, but the reduction largely saturates at about 0.3 eV for x >= 0.083. We also report preliminary results on the formation energy and electronic structure of O vacancies in TiNxO2-x-δ, and on interactions and complexes of these defects.
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Cobalt-doped titanium dioxide, or CTO, has emerged in the past 2 years as a semiconducting, transparent, room-temperature ferromagnet. Very recently it has been shown that the magnetism in CTO often originates in surface nanoparticles or... more
Cobalt-doped titanium dioxide, or CTO, has emerged in the past 2 years as a semiconducting, transparent, room-temperature ferromagnet. Very recently it has been shown that the magnetism in CTO often originates in surface nanoparticles or Co-rich regions that have a much-enhanced substitutional Co content up to 40% of Ti sites, so that magnetic CTO is not a true dilute magnetic semiconductor (DMS), but rather a fairly high-density spin system. In this work we describe a computational study of Co-rich CTO using the generalized gradient approximation to the density functional theory within the supercell model. Our total energy calculations show a strong tendency for Co-atom clustering or segregation on Ti sites. There is also a strong tendency for the oxygen vacancies to form complexes with the Co atoms. In addition, we find that the oxygen stoichiometry plays an essential role in determining the system's magnetic order. The largest ordered moments require at least enough oxygen vacancies to put all of the Co atoms in the +2 charge state, as they indeed appear to be experimentally, so that the conventional DMS mechanism could only apply via n-type carriers. We find a small but not negligible spin density associated with Ti atoms near the vacancy sites, suggesting an F-center-mediated interaction between the much larger Co moments. We also present experimental data showing that the ferromagnetic remanence and coercive field increase with the n-type conductivity.
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We describe calculations of the formation and hopping energies of hole polarons (holes self-consistently localized in lattice distortions) in the wide-bandgap ionic materials LaBr3 and CsI. Both one-center (breathing mode) and two center... more
We describe calculations of the formation and hopping energies of hole polarons (holes self-consistently localized in lattice distortions) in the wide-bandgap ionic materials LaBr3 and CsI. Both one-center (breathing mode) and two center (anion dimer, also known as Vk center) polarons were treated. The LDA+U method based on the VASP code was employed, since standard DFT methods often fail to represent localized electronic states in solids. We used a 72-atom supercell of the UCl3 structure for LaBr3, and a 54-atom CsCl-structure unit cell for CsI. We attempt to correlate differences in electronic transport between these two compounds with different energy nonproportionality behavior that they exhibit as Ce-activated scintillators in gamma-ray spectroscopy.
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We present DFT calculations of the total energies and equations of state of the monoclinic, tetragonal, cubic, orthorhombic-I (Pbca) and orthorhombic-II (cotunnite)-structure phases of zirconia and hafnia. We find that the accuracy of the... more
We present DFT calculations of the total energies and equations of state of the monoclinic, tetragonal, cubic, orthorhombic-I (Pbca) and orthorhombic-II (cotunnite)-structure phases of zirconia and hafnia. We find that the accuracy of the LDA approximation is not sufficient and that GGA corrections are critical to obtain low-temperature phase transitions under pressure that are consistent with experiment, i.e., (monoclinicdiamondsuit orthorhombic-I diamondsuit cotunnite). The GGA values of the bulk modulus of the cotunnite phase were found to be 251 and 259 GPa for ZrO2 and HfO_2, respectively. We introduce a new population analysis scheme in which atomic radii are adapted to the actual charge distribution in the material. The results indicate that the effective atomic radius of Hf is smaller than that of Zr, which is a drastic manifestation of the relativistic lanthanide contraction. The population analysis demonstrates that ionicity: (i) increases from the monoclinic to the cotunnite phase, and (ii) is larger for HfO2 than for ZrO_2. This variable ionicity may be the reason why LDA fails to describe the relative stability of different polymorphs. The bandgap and heat of formation are also larger for monoclinic HfO2 than for ZrO2 by 0.60 eV and 0.60 eV/formula unit, respectively. The tetragonal phase, which often exists as a metastable phase at ambient conditions, has a bandgap larger than the monoclinic phase by 0.35 and 0.65 eV for ZrO2 and HfO_2, respectively.
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Periodic HartreeâFock total energy calculations on two-dimensionally periodic slabs have been used to predict the equilibrium geometry of a monolayer of carbon monoxide molecules adsorbed on the nonpolar (10{bar 1}0) surface of ZnO. Two... more
Periodic HartreeâFock total energy calculations on two-dimensionally periodic slabs have been used to predict the equilibrium geometry of a monolayer of carbon monoxide molecules adsorbed on the nonpolar (10{bar 1}0) surface of ZnO. Two physisorbed (or weakly chemisorbed) minimum energy configurations are found. In one the CO molecules adsorb with their oxygen atoms coordinated to surface Zn atoms, while in the other the carbon atoms are coordinated to surface Zn atoms. The two calculated minima are very close in energy. In the second geometry, the CâZn {open_quote}{open_quote}bond{close_quote}{close_quote} and the CâO bond make angles of 32.5° and 39.5° with the surface normal, and the intramolecular bond shortens slightly from its free value in reasonable agreement with experimental results. No binding of CO to the surface oxygen atoms is predicted. Surface-related changes in the vibrational frequencies for the adsorbed molecules agree reasonably well with infrared spectroscopic data, and the {open_quote}{open_quote}carbon-down{close_quote}{close_quote} binding energy of the molecule with the surface is in good agreement with thermal desorption data (though electron correlation effects have to be included in the calculation to obtain acceptable results for low surface coverage). {copyright} {ital 1996 American Institute of Physics.}
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The phenomenology and present theoretical understanding of energy nonlinearity (nonproportionality) in radiation detection materials is reviewed, with emphasis on gamma-ray spectroscopy. Scintillators display varying degrees and patterns... more
The phenomenology and present theoretical understanding of energy nonlinearity (nonproportionality) in radiation detection materials is reviewed, with emphasis on gamma-ray spectroscopy. Scintillators display varying degrees and patterns of nonlinearity, while semiconductor detectors are extremely linear, and gas detectors show a characteristic form of nonproportionality associated with core levels. The relation between nonlinear response (to both primary particles and secondary electrons)
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We have studied the nonpolar (110) surface of the ternary chalcopyrite semiconductor CuInSe2 (CIS) by means of the local density approximation with ultrasoft pseudopotentials and plane waves. The surface relaxation is found to be... more
We have studied the nonpolar (110) surface of the ternary chalcopyrite semiconductor CuInSe2 (CIS) by means of the local density approximation with ultrasoft pseudopotentials and plane waves. The surface relaxation is found to be analogous to that of (110) surfaces of binary zinc-blende semiconductors, with surface cations sinking into the surface and anions displaced outwards by a rotation of surface bonds, but with added complexity due to the two chemically distinct cations. For CIS we define two surface layer rotation angles ω1 and ω2 describing the displacement of the Cu and In atoms respectively. At the energy minimum, we find relatively large rotations of ω1 = 36.1^o and ω2 = 38.7^o. The (110) surface of CIS thus behaves more similarly to zinc-blende CuCl and CuBr (ω ≈ 40^o)than to, for example, ZnSe (ω ≈ 23^o). The relaxed surface energy is 0.523 J/m^2 versus 0.859 J/m^2 for the unrelaxed surface. The electronic density of states and charge density will be described and compared for bulk CIS and its unrelaxed and relaxed (110) surface. Possible implications for photovoltaic device properties will be discussed.
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The causes of energy nonlinearity (nonproportionality) in gamma-ray spectroscopy of scintillators have not been fully explained quantitatively, but are believed to involve the spatial density of thermalized electrons and holes, their... more
The causes of energy nonlinearity (nonproportionality) in gamma-ray spectroscopy of scintillators have not been fully explained quantitatively, but are believed to involve the spatial density of thermalized electrons and holes, their transport and interactions, and competition between radiative and nonradiative recombination. Here, we relate electron-hole density to the initial ray's energy through expressions for the stopping power and distance, and then attempt to fit some "plateau-type" (e.g. BaF 2, Lu 2SiO 5, etc.) light curves via competing radiative and nonradiative processes obeying different energy power laws. We find that reasonable power laws and the assumption of a uniform energy density in the excited region lead to a fairly good agreement with many experimental curves. We then show that a simple approximation for averaging over regions of different excitation density leads to improved agreement with experiment, at the expense of making it more difficult to uncover the underlying kinetics from the experimental data. These considerations should carry over to more sophisticated models or simulations of scintillation processes.
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LDA and GGA calculations for high-pressure phase transitions in ZnO and MgO. John E. Jaffe, James A. Snyder, Zijing Lin, and Anthony C. Hess Materials Sciences Department, Pacific Northwest Laboratory, Richland, Washington 99352. ...
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Liquid metallic hydrogen, in a fully dissociated state, is predicted at certain densities to pass from dirty to clean and from type II to type I superconducting behavior as temperature is lowered. Previously announced in STAR as N82-29374
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Using the density functional supercell approach, we have calculated the formation and ionization energies of several native defects and the isoelectronic oxygen impurity in CdTe. Point defects include the Cd vacancy, Te-on-Cd antisite,... more
Using the density functional supercell approach, we have calculated the formation and ionization energies of several native defects and the isoelectronic oxygen impurity in CdTe. Point defects include the Cd vacancy, Te-on-Cd antisite, and the substitutional O on a Te site. We also considered Zn on a Cd site as a model for Cd_1-xZn_xTe (CZT) at low Zn concentration. In addition we studied complexes of the Cd vacancy with all the other point defects. Complex formation is found to be energetically favorable in most cases and alters the defect gap levels significantly. We discuss the implications for doping, trap states and Fermi level pinning in CdTe and CZT gamma-ray detector material.
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ZnO, which normally occurs in the hexagonal wurtzite structure, can be transformed to the cubic rocksalt (NaCl) structure by the application of high pressure; this cubic phase has been reported to be metastable at atmospheric pressure.... more
ZnO, which normally occurs in the hexagonal wurtzite structure, can be transformed to the cubic rocksalt (NaCl) structure by the application of high pressure; this cubic phase has been reported to be metastable at atmospheric pressure. The band structure of this phase is calculated by the ab initio correlated Hartree-Fock method. Not surprisingly, the band structure of rocksalt ZnO is very similar to that of CdO, which has the same crystal structure; we present a band-structure calculation for CdO, which we believe is more accurate than any in the literature. A hallmark of these band structures is that the valence-band maximum is not at the center of the Brillouin zone, in contrast to the situation in tetrahedrally coordinated II-VI semiconductors. We confirm by direct calculation that this peculiarity of the band structure is a consequence of the hybridization of oxygen 2p-derived orbitals with Zn 3d or Cd 4d states, combined with octahedral point symmetry.
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Using first-principles density functional theory, we have modeled the atomic, electronic and magnetic structure of epitaxial interfaces between the corundum-structure oxides α -Fe_2O3 (hematite) and α -Cr_2O3 (eskolaite) in the hexagonal... more
Using first-principles density functional theory, we have modeled the atomic, electronic and magnetic structure of epitaxial interfaces between the corundum-structure oxides α -Fe_2O3 (hematite) and α -Cr_2O3 (eskolaite) in the hexagonal (0001) basal plane. Our model was a superlattice with a period of about 27.5Åcorresponding to the shortest-period superlattice considered in a recent series of experiments[1]. Two different epitaxial interface structures are possible: (i) an oxygen plane separating an Fe double layer from a Cr double layer, which we refer to as the ``oxygen-divided'' interface; and (ii) a metal double layer split between Fe and Cr, which we call the ``split-metal'' interface. We found that these two structures are close in total energy but have distinct electronic and magnetic structure and different band offsets: 0.4 eV for the oxygen-divided interface and 0.6 eV for the split-metal interface. This may explain the non-commutative band offset seen in the experiments[1] on this system. [1] S. A. Chambers, Y. Liang, and Y. Gao, Phys. Rev. B 61, 13223 (2000).
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Chemisorption of atomic and molecular hydrogen on the nonpolar ZnO (10\overline10) surface has been studied by means of the ab initio Hartree-Fock method in the two-dimensionally periodic slab model. Both the surface and the hydrogen... more
Chemisorption of atomic and molecular hydrogen on the nonpolar ZnO (10\overline10) surface has been studied by means of the ab initio Hartree-Fock method in the two-dimensionally periodic slab model. Both the surface and the hydrogen adsorption geometry were optimized for hydrogen adsorption near surface zinc and oxygen sites. We find adsorption energies to be substantial for heterolytic dissociation of hydrogen molecules. ZnO surface derelaxation makes an important contribution to the binding energy. A posteriori correlation corrections to the total energies were calculated, and we discuss the dependence of adsorption properties on surface coverage. Vibrational frequencies of stretching H-Zn and O-H bonds were also calculated.
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We have used all-electron Gaussian-basis periodic density-functional calculations to predict the atomic geometry of the nonpolar (10\overline10) surface of the wurtzite-structure mineral bromellite (beryllium oxide). Compared to the... more
We have used all-electron Gaussian-basis periodic density-functional calculations to predict the atomic geometry of the nonpolar (10\overline10) surface of the wurtzite-structure mineral bromellite (beryllium oxide). Compared to the surface relaxation in more covalent materials such as CdS we find in BeO a reduced tilting of the surface dimers and an enhanced contraction of the surface and back bonds. We discuss the relative roles of ionicity and double bond character of the surface bonds in producing this behavior.
Periodic Hartree-Fock total energy calculations on two-dimensionally periodic slabs have been used to predict the equilibrium geometry of a monolayer of carbon monoxide molecules adsorbed on the nonpolar (101¯0) surface of ZnO. Two... more
Periodic Hartree-Fock total energy calculations on two-dimensionally periodic slabs have been used to predict the equilibrium geometry of a monolayer of carbon monoxide molecules adsorbed on the nonpolar (101¯0) surface of ZnO. Two physisorbed (or weakly chemisorbed) minimum energy configurations are found. In one the CO molecules adsorb with their oxygen atoms coordinated to surface Zn atoms, while in the other the carbon atoms are coordinated to surface Zn atoms. The two calculated minima are very close in energy. In the second geometry, the C-Zn ``bond'' and the C-O bond make angles of 32.5° and 39.5° with the surface normal, and the intramolecular bond shortens slightly from its free value in reasonable agreement with experimental results. No binding of CO to the surface oxygen atoms is predicted. Surface-related changes in the vibrational frequencies for the adsorbed molecules agree reasonably well with infrared spectroscopic data, and the ``carbon-down'' binding energy of the molecule with the surface is in good agreement with thermal desorption data (though electron correlation effects have to be included in the calculation to obtain acceptable results for low surface coverage).
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ABSTRACT
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The Cu overlayer adsorbed on CaO(100) was studied at the density functional level of theory. Following an experimental suggestion, we examined a complete c(1x1) structure with copper atoms adsorbed on every hollow site of CaO(100). The... more
The Cu overlayer adsorbed on CaO(100) was studied at the density functional level of theory. Following an experimental suggestion, we examined a complete c(1x1) structure with copper atoms adsorbed on every hollow site of CaO(100). The binding energy/atom for this structure is 3.19 eV. However, another c(1x1) structure proposed by us, with copper atoms on every surface Ca and O
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A primary objective in heterogeneous catalysis science is to correlate the atomic level properties of the catalysts to their observed macroscopic behavior. A wide variety of surface techniques and sophisticated theoretical approaches have... more
A primary objective in heterogeneous catalysis science is to correlate the atomic level properties of the catalysts to their observed macroscopic behavior. A wide variety of surface techniques and sophisticated theoretical approaches have been employed to realize this goal. Ab initio calculations based on a density-functional all electron approach using localized Gaussian basis sets have been used by us to
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Gaussian-basis LDA and GGA calculations for alkali-metal equations of state. John E. Jaffe, Zijing Lin, and Anthony C. Hess Materials Sciences Department, Pacific Northwest Laboratory, Richland, Washington 99352. Received 17 November 1997... more
Gaussian-basis LDA and GGA calculations for alkali-metal equations of state. John E. Jaffe, Zijing Lin, and Anthony C. Hess Materials Sciences Department, Pacific Northwest Laboratory, Richland, Washington 99352. Received 17 November 1997 ...
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Defect-induced nonpolar-to-polar transition at the surface of chalcopyrite semiconductors. John E. Jaffe William R. Wiley Environmental Molecular Sciences Laboratory Pacific Northwest National Laboratory, Richland, Washington 99352. ...
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... 2. Correlation between the observed (Refs. 1-3) and calculated (using the CTB model) anion displacement parameters for the ternary chalcopyrites. The uncertain data for the telurides is omitted. Multiple arrows denote various... more
... 2. Correlation between the observed (Refs. 1-3) and calculated (using the CTB model) anion displacement parameters for the ternary chalcopyrites. The uncertain data for the telurides is omitted. Multiple arrows denote various experimental determinations. ...
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Theory of the band-gap anomaly in ABC 2 chalcopyrite semiconductors. JE Jaffe and Alex Zunger Solar Energy Research Institute, Golden, Colorado 80401. ... 58, 357 (1973) [INSPEC][CAS]. AA Vaipolin, NA Goryusova, LI Kleshchinskii, GV... more
Theory of the band-gap anomaly in ABC 2 chalcopyrite semiconductors. JE Jaffe and Alex Zunger Solar Energy Research Institute, Golden, Colorado 80401. ... 58, 357 (1973) [INSPEC][CAS]. AA Vaipolin, NA Goryusova, LI Kleshchinskii, GV Loshakova, and ED Osmanov, Phys. ...
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Résumé/Abstract La structure électronique de six semiconducteurs de type chalcopyrite ternaire à base de cuivre, est calculée de manière autocohérente dans le formalisme de la fonctionnelle de densité. On analyse les tendances chimiques... more
Résumé/Abstract La structure électronique de six semiconducteurs de type chalcopyrite ternaire à base de cuivre, est calculée de manière autocohérente dans le formalisme de la fonctionnelle de densité. On analyse les tendances chimiques dans les structures de ...
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... Rev. Lett. 59, 1160 (1987). 15W. K. Kwok, Ph.D. thesis, Purdue University, West Lafayette, Indiana, 1987. 16A. J. Panson et al., Phys. Rev. B 35, 8774 (1987). 17M. ... 21S. W. Tozer, AW Kleinasser, T. Penny, D. Kaiser, and F.... more
... Rev. Lett. 59, 1160 (1987). 15W. K. Kwok, Ph.D. thesis, Purdue University, West Lafayette, Indiana, 1987. 16A. J. Panson et al., Phys. Rev. B 35, 8774 (1987). 17M. ... 21S. W. Tozer, AW Kleinasser, T. Penny, D. Kaiser, and F. Holtzberg, Phys. Rev. Lett. ...