Search results for "ELECTRONIC STRUCTURE"

Atomic and Electronic Structure of the Corundum (0001) Surface

1996

AbstractThe electronic structure and geometry of the Al terminated corundum (0001) surface were studied using a slab model within the ab-initio Hartree-Fock technique. The distance between the top Al plane and the next O basal plane is found to be considerably reduced on relaxation (by 0.57 Å, i.e. by 68% of the corresponding interlayer distance in the bulk). An interpretation of experimental photoelectron spectra (UPS Hel) and metastable impact electron spectra (MIES) is given. Calculated projected densities of states exhibit a strong dependence on the relaxation of surface atoms.

Electronic structure and thermodynamic stability of double-layeredSrTiO3(001)surfaces:Ab initiosimulations

2007

Using the B3PW hybrid exchange-correlation functional within density-functional theory and employing Gaussian-type basis sets, we calculated the atomic and electronic structures and thermodynamic stability of three double-layered (DL) SrTiO3(001) surfaces: (i) SrO-terminated, (ii) TiO2-terminated, and (iii) (2×1) reconstruction of TiO2-terminated SrTiO3(001) recently suggested by Erdman et al. [Nature (London) 419, 55 (2002)]. A thermodynamic stability diagram obtained from first-principles calculations shows that regular TiO2- and SrO-terminated surfaces are the most stable. The stability regions of (2×1) DL TiO2- and DL SrO-terminated surfaces lie beyond the precipitation lines of SrO and…

Calculations of atomic and electronic structure for (100) surfaces of SrTiO3 perovskite

2002

AbstractWe present and discuss main results of the calculations for the surface relaxation and rumpling of SrTiO3 surfaces with TiO2 and SrO terminations using a wide variety of methods of modern computational physics and chemistry, including the shell model (SM) and ab initio methods based on Hartree-Fock (HF) and Density Functional Theory (DFT). The HF and DFT formalisms with different exchange-correlation functionals are implemented into Crystal-98 computer code using a Gaussian-type basis set. We demonstrate that a hybrid B3PW formalism gives the best results for the bulk SrTiO3 properties. Results are compared with previous ab initio plane-wave LDA calculations and LEED experiments. Ou…

Surface segregation trends in transition metal alloys

2013

In this work, we revisit the problem of predicting the surface segregation trends in binary transition metal alloys from the knowledge of the basic features of the pure component $d$-band electronic structure within tight-binding approximation. In contrast to previous trend studies, the present one includes, within the fourth-moment approximation (FMA) of the tight-binding scheme, both the difference in the average band energies (diagonal disorder) and the difference in the band widths (off-diagonal disorder) of the two components. We show that treating on the same footing these two effects is essential for a correct prediction of surface segregation. The presented study, giving a natural l…

Simulation of tungsten tip-Al(100) surface electronic structure through LCAO-LSD calculations

1997

Effect of H Adsorption on the Magnetic Properties of an Fe Island on a W(110) Surface

2019

<p>Low-dimensional materials, such as ultrathin films, nanoislands and wires, are actively being researched due to their interesting magnetic properties and possible technological applications for example in high density data storage. Results of calculations of an Fe nanoisland on a W(110) support are presented here with particular focus on the effect of hydrogen adsorption on its magnetic properties. This is an important consideration since hydrogen is present even under ultra-high vacuum conditions. The calculations are based on density functional theory within the generalized gradient approximation. The adsorption of H atoms is found to strongly decrease the magnetic moment of the …

The electronic and atomic structure of SrTiO3, BaTiO3, and PbTiO3(001) surfaces: Ab initio DFT/HF hybrid calculations

2005

In our first-principles study, the electronic properties of the (001) surfaces of three key perovskite crystals, namely SrTiO"3 (STO), BaTiO"3 (BTO), and PbTiO"3 (PTO), have been calculated by means of the density functional theory (DFT) using the exchange-correlation functional containing ''hybrid'' of the non-local Hartree-Fock (HF) exchange, DFT exchange, and Generalized Gradient Approximation (GGA) correlation functionals, commonly known as B3PW. Such a technique allows us to get the optical bulk band gap very close to experiment unlike previous calculations of perovskites. Special attention is paid to careful calculations of the surface rumpling and change of the distances between thre…

Electronic structure trends of Möbius graphene nanoribbons from minimal-cell simulations

2014

Investigating topological effects in materials requires often the modeling of material systems as a whole. Such modeling restricts system sizes, and makes it hard to extract systematic trends. Here, we investigate the effect of M\"obius topology in the electronic structures of armchair graphene nanoribbons. Using density-functional tight-binding method and minimum-cell simulations through revised periodic boundary conditions, we extract electronic trends merely by changing cells' symmetry operations and respective quantum number samplings. It turns out that for a minimum cell calculation, once geometric and magnetic contributions are ignored, the effect of the global topology is unexpectedl…

Vacancy Defects in Ga2O3: First-Principles Calculations of Electronic Structure

2021

This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP08856540) as well as by the Latvian research council via the Latvian National Research Program under the topic ?High-Energy Physics and Accelerator Technologies?, Agreement No: VPP-IZM-CERN-2020/1-0002 for A.I. Popov. In addition, J. Purans is grateful to the ERAF project 1.1.1.1/20/A/057 while A. Platonenko was supported by Latvian Research Council No. LZP-2018/1-0214. The authors thank A. Lushchik and M. Lushchik for many useful discussions. The research was (partly) performed in the Institute of Solid State Physics, University of Latvia ISSP UL. ISSP UL as…

Ligand engineering in Cu(ii) paddle wheel metal–organic frameworks for enhanced semiconductivity

2020

We report the electronic structure of two metal-organic frameworks (MOFs) with copper paddle wheel nodes connected by a N2(C2H4)3 (DABCO) ligand with accessible nitrogen lone pairs. The coordination is predicted, from first-principles density functional theory, to enable electronic pathways that could facilitate charge carrier mobility. Calculated frontier crystal orbitals indicate extended electronic communication in DMOF-1, but not in MOF-649. This feature is confirmed by bandstructure calculations and effective masses of the valence band egde. We explain the origin of the frontier orbitals of both MOFs based on the energy and symmetry alignment of the underlying building blocks. The effe…