1. 
 Laukkanen, P., et al.
(författare)

Bismuthstabilized c(2X6) reconstruction on a InSb(100) substrate Violation of the electron counting model
 2010

Ingår i: Physical Review B. Condensed Matter and Materials Physics.  10980121. ; 81:3

Tidskriftsartikel (refereegranskat)abstract
 By means of scanning tunneling microscopy/spectroscopy (STM/STS), photoelectron spectroscopy, and firstprinciples calculations, we have studied the bismuth (Bi) adsorbatestabilized InSb(100) substrate surface which shows a c(2X6) lowenergy electron diffraction pattern [thus labeled Bi/InSb(100)c(2X6) surface] and which includes areas with metallic STS curves as well as areas with semiconducting STS curves. The firstprinciples phase diagram of the Bi/InSb(100) surface demonstrates the presence of the Bistabilized metallic c(2X6) reconstruction and semiconducting (4X3) reconstruction depending on the chemical potentials, in good agreement with STS results. The existence of the metallic c(2X6) phase, which does not obey the electron counting model, is attributed to the partial prohibition of the relaxation in the direction perpendicular to dimer rows in the competing reconstructions and the peculiar stability of the Bistabilized dimer rows. Based on (i) firstprinciples phase diagram, (ii) STS results, and (iii) comparison of the measured and calculated STM and photoemission data, we show that the measured Bi/InSb(100)c(2X6) surface includes metallic areas with the stable c(2X6) atomic structure and semiconducting areas with the stable (4X3) atomic structure.


2. 
 Laukkanen, P., et al.
(författare)

Corelevel shifts of the c(8 x 2)reconstructed InAs(100) and InSb(100) surfaces
 2010

Ingår i: Journal of Electron Spectroscopy and Related Phenomena.  03682048. ; 177:1, s. 5257

Tidskriftsartikel (refereegranskat)abstract
 We have studied Instabilized c(8 2)reconstructed InAs(1 0 0) and InSb(1 0 0) semiconductor surfaces, which play a key role in growing improved IIIV interfaces for electronics devices, by corelevel photoelectron spectroscopy and firstprinciples calculations. The calculated surface corelevel shifts (SCLSs) for the zeta and zeta a models, which have been previously established to describe the atomic structures of the IIIV(1 00)c(8 x 2) surfaces, yield hitherto not reported interpretation for the As 3d, In 4d, and Sb 4d corelevel spectra of the IIIV(1 00)c(8 x 2) surfaces, concerning the number and origins of SCLSs. The fitting analysis of the measured spectra with the calculated zeta and zeta a SCLS values shows that the InSb spectra are reproduced by the zeta SCLSs better than by the zeta a SCLSs. Interestingly, the zeta a fits agree better with the InAs spectra than the zeta fits do, indicating that the zeta a model describes the InAs surface better than the InSb surface. These results are in agreement with previous Xray diffraction data. Furthermore, an introduction of the completescreening model, which includes both the initial and final state effects, does not improve the fitting of the InSb spectra, proposing the suitability of the initialstate model for the SCLSs of the IIIV(1 0 0)c(8 x 2) surfaces. The found SCLSs are discussed with the ab initio onsite charges.


3. 
 Punkkinen, M. P. J., et al.
(författare)

Bismuthstabilized (2x1) and (2x4) reconstructions on GaAs(100) surfaces : Combined firstprinciples, photoemission, and scanning tunneling microscopy study
 2008

Ingår i: Physical Review B. Condensed Matter and Materials Physics.  10980121. ; 78:19

Tidskriftsartikel (refereegranskat)abstract
 Bismuth adsorbatestabilized (2x1) and (2x4) reconstructions of the GaAs(100) surfaces have been studied by firstprinciples calculations, valenceband and corelevel photoelectron spectroscopies, and scanning tunneling microscopy. It is demonstrated that large Bi atom size leads to the formation of the pseudogap at the Fermi energy and to the lower energy of an adsorbatederived surface band, which contributes to the stabilization of the exceptional Bi/GaAs(100)(2x1) reconstruction. It is proposed that the Bi/GaAs(100)(2x4) reconstructions include asymmetric mixed BiAs dimers, in addition to the BiBi dimers. Based on the calculations, we solve the atomic origins of the surface corelevel shifts (SCLSs) of the Bi 5d photoemission spectra from the Bi/GaAs(100)(2x4) surfaces. This allows for resolving the puzzle related to the identification of two SCLS components often found in the measurements of the Bi 5d and Sb 4d corelevel emissions of the Bi/IIIV and Sb/IIIV(100)(2x4) surfaces. Finally, the reason for the absence of the common (2x4)beta 2 structure and additional support for the stability of the (2x1) structure on the Bi/IIIV(100) surfaces are discussed in terms of Bi atom size and subsurface stress.


4. 
 Lang, J. J. K., et al.
(författare)

Tinstabilized (1 x 2) and (1 x 4) reconstructions on GaAs(100) and InAs(100) studied by scanning tunneling microscopy, photoelectron spectroscopy, and ab initio calculations
 2011

Ingår i: Surface Science.  00396028. ; 605:910, s. 883888

Tidskriftsartikel (refereegranskat)abstract
 Tin (Sn) induced (1 x 2) reconstructions on GaAs(100) and InAs(100) substrates have been studied by low energy electron diffraction (LEED), photoelectron spectroscopy, scanning tunneling microscopy/spectroscopy (STM/STS) and ab initio calculations. The comparison of measured and calculated STM images and surface corelevel shifts shows that these surfaces can be well described with the energetically stable building blocks that consist of SnIII dimers. Furthermore, a new Sninduced (1 x 4) reconstruction was found. In this reconstruction the occupied dangling bonds are closer to each other than in the more symmetric (1 x 2) reconstruction, and it is shown that the (1 x 4) reconstruction is stabilized as the adatom size increases.


5. 
 Abrikosov, I. A., et al.
(författare)

Valenceband hybridization and core level shifts in random AgPd alloys
 2001

Ingår i: Physical Review Letters.  00319007. ; 8717:17

Tidskriftsartikel (refereegranskat)abstract
 Firstprinciples calculations of the corelevel binding energy shifts (CLS) for 3d innercore electrons of Ag and Pd in fcc AgPd alloy were carried out within the complete screening picture, which includes both initial and final state effects. These allo


6. 
 Ahuja, R., et al.
(författare)

Electronic and optical properties of lead iodide
 2002

Ingår i: Journal of Applied Physics.  00218979. ; 92:12, s. 72197224

Tidskriftsartikel (refereegranskat)abstract
 Electronic and optical properties of lead iodide were studied experimentally using absorption, transmission, ellipsometry, and theoretically using a fullpotential linear muffintinorbital method. The samples were mounted in a closedcycle helium refrigeration system and studied at temperatures between 10 and 300 K. Bandgap energy of lead iodide was measured as a function of temperature using optical absorption. Calculations showed that there was a small anisotropy in optical properties of lead iodide, and dielectric function calculations agreed well with experiments.


7. 
 Ahuja, Rajeev, et al.
(författare)

Optical properties of 4HSiC
 2002

Ingår i: Journal of Applied Physics.  00218979. ; 91:3, s. 20992103

Tidskriftsartikel (refereegranskat)abstract
 The optical band gap energy and the dielectric functions of ntype 4HSiC have been investigated experimentally by transmission spectroscopy and spectroscopic ellipsometry and theoretically by an ab initio fullpotential linear muffintinorbital method. We present the real and imaginary parts of the dielectric functions, resolved into the transverse and longitudinal photon moment a, and we show that the anisotropy is small in 4HSiC. The measurements and the calculations fall closely together in a wide range of energies. © 2002 American Institute of Physics.


8. 
 Andersson, David A., et al.
(författare)

Redox properties of CeO2MO2 MO2 (M=Ti, Zr, Hf or Th) solid solutions from first principles calculations
 2007

Ingår i: Applied Physics Letters.  00036951. ; 90:3, s. 031909

Tidskriftsartikel (refereegranskat)abstract
 The authors have used density functional theory calculations to investigate how the redox thermodynamics and kinetics of CeO2 are influenced by forming solid solutions with TiO2, ZrO2, HfO2, and ThO2. Reduction is facilitated by dissolving TiO2 (largest improvement), HfO2, or ZrO2 (least improvement), while ThO2 makes reduction slightly more difficult. The migration barrier is much lower in the neighborhood of a Ti (largest decrease), Hf, or Zr (least decrease), while the binding energy of solute ions and vacancies increases in the same sequence. They rationalize the properties of ceria solid solutions in terms of defect cluster relaxations.


9. 
 Belonoshko, Anatoly B., et al.
(författare)

Quenching of bccFe from high to room temperature at highpressure conditions : a molecular dynamics simulation
 2009

Ingår i: NEW JOURNAL OF PHYSICS.  13672630. ; 11, s. 093039

Tidskriftsartikel (refereegranskat)abstract
 The new hightemperature (T), highpressure (P), bodycentered cubic (bcc) phase of iron has probably already been synthesized in recent diamond anvil cell (DAC) experiments (Mikhaylushkin et al 2007 Phys. Rev. Lett. 99 165505). These DAC experiments on iron revealed that the highPT phase on quenching transforms into a mixture of closepacked phases. Our molecular dynamics simulation and structural analysis allow us to provide a probable interpretation of the experiments. We show that quenching of the highPT bcc phase simulated with the embeddedatom model also leads to the formation of the mixture of closepacked phases. Therefore, the assumption of the stability of the highPT bcc iron phase is consistent with experimental observation.


10. 
 Bleskov, I. D., et al.
(författare)

Ab initio calculations of elastic properties of Ru1xNixAl superalloys
 2009

Ingår i: Applied Physics Letters.  00036951. ; 94:16

Tidskriftsartikel (refereegranskat)abstract
 Ab initio total energy calculations based on the exact muffintin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1xNixAl alloys. We have found that the elastic constants C' and C11 exhibit pronounced peculiarities near the concentration of about 40 at. % Ni, which we ascribe to electronic topological transitions. Our suggestion is supported by the Fermi surface calculations in the whole concentration range. Results of our calculations show that one can design RuNiAl alloys substituting Ru by Ni (up to 40 at. %) with almost invariable elastic constants and reduced density.

