Density functional theory in the generalized gradient approximation has been used to calculate the total energy and model the atomic and electronic structures of thin FeSi films with CsCl type ...lattice and γ-FeSi
2
films with CaF
2
fluorite type lattice on a Si(111) surface. It is shown that, upon the adsorption of two monolayers of iron atoms on Si(111), the most energetically favorable process is the growth of a γ-FeSi
2
film with CaF
2
type structure. The electronic structure of a silicide film formed upon the adsorption of one monolayer of iron atoms exhibits features that are characteristic of both FeSi and γ-FeSi
2
. The density of states calculated for the γ-FeSi
2
well agrees with the experimental photoemission spectra reported in the literature.
The ratio of the electron and muon widths of the J/ psi J/ psi meson has been measured using direct J/ psi J/ psi decays in the KEDR experiment at the VEPP-4M electron-positron collider. The result ...Gamma e+e-(J/ psi )/ Gamma mu + mu -(J/ psi )=1.0022 plus or minus 0.0044 plus or minus 0.0048(0.65%) is in good agreement with the lepton universality. The experience collected during this analysis will be used for J/ psi J/ psi lepton width determination with up to 1% accuracy.
Adsorption of trimethylphosphine (TMP) on a Si(111)-(7×7) surface was studied using scanning tunneling microscopy (STM), high-resolution electron energy loss spectroscopy (HREELS), and theoretical ...calculations. It was found from STM and HREELS that most of the TMP molecules are adsorbed molecularly on center adatom sites at room temperature. A semi-empirical calculation (AM1 method) verified that this is energetically favorable. It is also found that one of the protrusions (unoccupied state images) on the center adatom site moves to the rest atom site and three protrusions (occupied state images) appear on the corner and center adatom sites in the second scan (interval of a few minutes). The results of a theoretical calculation indicate that adsorption of the three CH
3 groups and the P atom on the adatom and rest atom sites, respectively, is energetically favorable. This explains the STM images well. The HREELS result suggests that the CH
3 group is split off and dissociated into CH
2 (or CH) and H upon heating the sample. The result of the theoretical calculation shows that the dissociation of CH
3 into CH
2 and H is energetically preferable when CH
2 is bridged between an Si adatom and an Si atom in the second layer and H is on the rest atom site.
Atomic dynamics of In nanoclusters on Si ( 100 ) Saranin, A. A.; Zotov, A. V.; Kuyanov, I. A. ...
Physical review. B, Condensed matter and materials physics,
09/2006, Volume:
74, Issue:
12
Journal Article
Using ab initio (Hartree–Fock and local density approximation) and semiempirical (Austin Model 1) calculations, we studied the energetics and electronic structures of NB and NP complexes. We found ...that these complexes are electrically inactive. The formation energies are 1.6 eV for the NB coupling and 2.4 eV for the NP pairing. The N–P and N–B interatomic equilibrium distances are about 3.5 Å for both complexes.
The Austin Model 1 (AM1) semi-empirical numerical method combined with the geometry optimization procedure was used to study the energetics of P–Si and P–P dimers on the Si(100)-2×1 surface in a ...cluster approach. It has been found that the P–Si dimers are more preferable energetically. The energy profit depends on the cluster size and is about 0.8–0.9 eV for large clusters.
The Austin Model 1 semi-empirical method combined with geometry optimization procedure was used to study atomic and electronic structures of nanoscale silica particles containing up to 192 atoms (64 ...Si and 128 O). Twofold Si–O rings were found to dominate in nanometer sized particles. The fraction of larger rings increases with increasing particle sizes. Bond length and bond angle distributions were calculated. The shortest Si–O, O–O and Si–Si interatomic distances are approximately 1.7, 3.0 and 3.3 Å, respectively. Average O–Si–O and Si–O–Si bond angles are approximately 110
∘ and 130
∘. Average electronic energy band gap is 6.9 eV.
A computationally inexpensive semiempirical numerical method (AM1) has been evaluated for its usefulness as a mean of providing fast estimates of geometries and energetics of defects and impurities ...in silicon. As a case study we considered adsorption of Al (a typical sp-bonded impurity) in the Al–Si(111)
3
×
3
system and chaotic Si and Al deposition onto the Si(100)2×1 substrate. In spite of the simplicity of the approach, salient features of these systems are properly described. In addition, we find that surface roughening and destruction of the substrate 2×1 dimerization during low-temperature Si deposition is a result of strong Si–Si interaction. Chaotic Al adatoms do not break the surface Si dimers. This is a qualitative difference which can be easily verified experimentally.
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