51 research outputs found
The theoretical DFT study of electronic structure of thin Si/SiO2 quantum nanodots and nanowires
The atomic and electronic structure of a set of proposed thin (1.6 nm in
diameter) silicon/silica quantum nanodots and nanowires with narrow interface,
as well as parent metastable silicon structures (1.2 nm in diameter), was
studied in cluster and PBC approaches using B3LYP/6-31G* and PW PP LDA
approximations. The total density of states (TDOS) of the smallest
quasispherical silicon quantum dot (Si85) corresponds well to the TDOS of the
bulk silicon. The elongated silicon nanodots and 1D nanowires demonstrate the
metallic nature of the electronic structure. The surface oxidized layer opens
the bandgap in the TDOS of the Si/SiO2 species. The top of the valence band and
the bottom of conductivity band of the particles are formed by the silicon core
derived states. The energy width of the bandgap is determined by the length of
the Si/SiO2 clusters and demonstrates inverse dependence upon the size of the
nanostructures. The theoretical data describes the size confinement effect in
photoluminescence spectra of the silica embedded nanocrystalline silicon with
high accuracy.Comment: 22 pages, 5 figures, 1 tabl
ΠΠΎΠΌΠΏΠ»Π΅ΠΊΡ ΡΠ΅ΡΡΡΠΈΠ°ΠΊΡΠΎΠ½Π° Ρ Mg(II): ΡΠΈΠ½ΡΠ΅Π·, ΡΡΡΡΠΊΡΡΡΠ°, ΡΠΏΠ΅ΠΊΡΡΠ°Π»ΡΠ½ΡΠ΅ ΠΈ Π°Π½ΡΠΈΠ±Π°ΠΊΡΠ΅ΡΠΈΠ°Π»ΡΠ½ΡΠ΅ ΡΠ²ΠΎΠΉΡΡΠ²Π°
Magnesium complex of ceftriaxone was obtained and characterized by atomic-emission and elemental analysis, TGA, FTIR and Raman spectroscopy, Xβray diffraction and density functional theory calculations. Ceftriaxone was coordinated to the magnesium ion by the oxygen of the triazine cycle in the 6th position, the nitrogen of the amine group of the thiazole ring, and oxygen atoms of the lactam carbonyl and carboxylate groups. The disodium salt of ceftriaxone and magnesium complex were screened for antibacterial activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosaΠΠΎΠ»ΡΡΠ΅Π½ ΠΈ ΠΎΡ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΠ·ΠΎΠ²Π°Π½ ΠΌΠ°Π³Π½ΠΈΠ΅Π²ΡΠΉ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡ ΡΠ΅ΡΡΡΠΈΠ°ΠΊΡΠΎΠ½Π° ΠΌΠ΅ΡΠΎΠ΄Π°ΠΌΠΈ
Π°ΡΠΎΠΌΠ½ΠΎ-ΡΠΌΠΈΡΡΠΈΠΎΠ½Π½ΠΎΠ³ΠΎ
ΠΈ ΡΠ»Π΅ΠΌΠ΅Π½ΡΠ½ΠΎΠ³ΠΎ Π°Π½Π°Π»ΠΈΠ·ΠΎΠ², Π’ΠΠ, ΠΠ- ΠΈ ΠΠ βΡΠΏΠ΅ΠΊΡΡΠΎΡΠΊΠΎΠΏΠΈΠΈ, Π Π€Π ΠΈ ΡΠ°ΡΡΠ΅ΡΠΎΠ²
ΡΠ΅ΠΎΡΠΈΠΈ ΡΡΠ½ΠΊΡΠΈΠΎΠ½Π°Π»Π° ΠΏΠ»ΠΎΡΠ½ΠΎΡΡΠΈ. Π¦Π΅ΡΡΡΠΈΠ°ΠΊΡΠΎΠ½ ΠΊΠΎΠΎΡΠ΄ΠΈΠ½ΠΈΡΡΠ΅ΡΡΡ ΠΊ ΠΈΠΎΠ½Ρ ΠΌΠ°Π³Π½ΠΈΡ ΡΠ΅ΡΠ΅Π· ΠΊΠΈΡΠ»ΠΎΡΠΎΠ΄
ΡΡΠΈΠ°Π·ΠΈΠ½ΠΎΠ²ΠΎΠ³ΠΎ ΡΠΈΠΊΠ»Π° Π² ΡΠ΅ΡΡΠΎΠΌ ΠΏΠΎΠ»ΠΎΠΆΠ΅Π½ΠΈΠΈ, Π°Π·ΠΎΡ Π°ΠΌΠΈΠ½ΠΎΠ³ΡΡΠΏΠΏΡ ΡΠΈΠ°Π·ΠΎΠ»ΡΠ½ΠΎΠ³ΠΎ ΡΠΈΠΊΠ»Π° ΠΈ Π°ΡΠΎΠΌΡ ΠΊΠΈΡΠ»ΠΎΡΠΎΠ΄Π°
ΠΊΠ°ΡΠ±ΠΎΠΊΡΠΈΠ»ΡΠ½ΠΎΠΉ ΠΈ Π»Π°ΠΊΡΠ°ΠΌΠ½ΠΎΠΉ Π³ΡΡΠΏΠΏ. ΠΠΈΠ½Π°ΡΡΠΈΠ΅Π²Π°Ρ ΡΠΎΠ»Ρ ΡΠ΅ΡΡΡΠΈΠ°ΠΊΡΠΎΠ½Π° ΠΈ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡ ΠΌΠ°Π³Π½ΠΈΡ Π±ΡΠ»ΠΈ
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½Ρ Π½Π° Π°Π½ΡΠΈΠ±Π°ΠΊΡΠ΅ΡΠΈΠ°Π»ΡΠ½ΡΡ Π°ΠΊΡΠΈΠ²Π½ΠΎΡΡΡ Π² ΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΠΈ Staphylococcus aureus, Escherichia
coli ΠΈ Pseudomonas aeruginos
The influence of size effect on the electronic and elastic properties of diamond films with nanometer thickness
The atomic structure and physical properties of few-layered oriented
diamond nanocrystals (diamanes), covered by hydrogen atoms from both sides are
studied using electronic band structure calculations. It was shown that energy
stability linear increases upon increasing of the thickness of proposed
structures. All 2D carbon films display direct dielectric band gaps with
nonlinear quantum confinement response upon the thickness. Elastic properties
of diamanes reveal complex dependence upon increasing of the number of
layers. All theoretical results were compared with available experimental data.Comment: 16 pages, 5 figures, 3 table
Two-Dimensional Lattices of VN: Emergence of Ferromagnetism and Half-Metallicity on Nanoscale
Π’Π΅ΠΊΡΡ ΡΡΠ°ΡΡΠΈ Π½Π΅ ΠΏΡΠ±Π»ΠΈΠΊΡΠ΅ΡΡΡ Π² ΠΎΡΠΊΡΡΡΠΎΠΌ Π΄ΠΎΡΡΡΠΏΠ΅ Π² ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΠΈΠΈ Ρ ΠΏΠΎΠ»ΠΈΡΠΈΠΊΠΎΠΉ ΠΆΡΡΠ½Π°Π»Π°.Two-dimensional (2D) ferromagnets with high spin-polarization ratio and high Curie temperature are crucial for developing next-generation spintronic nanodevices. Using first-principles calculations, we predict two polymorphic modifications (t-VN and h-VN) of 2D VN lattices that have robust intrinsic ferromagnetic properties and high Curie temperatures. Whereas t-VN has 99.9% of spin polarization at the Fermi level, h-VN possesses a half-metallic type of conductivity and keeps it after contact with semiconducting MoS2, which can be used as the substrate for h-VN synthesis and valley polarized contacts. Magnetocrystalline anisotropy energy of 2D VN polymorphs is found to be at least an order larger than those of Fe and Ni bulks. The phonon spectra and ab initio molecular dynamic simulation prove that 2D VN lattices have a high thermodynamic stability. These advantages demonstrate that the VN monolayers should be promising candidates for low-dimensional spintronic devices
Quantum Chemical Study of Atomic Structure and Spin States of the Cox(C60)n (x=1-8, n=1-3) Complex Nanoclusters
The main features of the local atomic structure of novel Con(C60)x (n=1-8, x=1-3) complexes and Con
clusters as well were studied using the ab initio GGA calculations for a set of low and high energy
isomers in different spin states. It is shown that high-spin low-symmetry structure of free-standing Con
clusters is determined by Jahn-Teller distortions. For the Co(C60)x (x=1-3) isomers the spin state S=1/2
is energetically preferable whereas the low energy isomers of Co2(C60)x (x=1-3) have an intermediate
spin state of S=1. The Ξ·2 (6-6 edge of C60) type of cobalt ion coordination is preferable for both n=1
and n=2 cases. The Ξ·2 (coordination with 6-5 edge) and even the Ξ·5 (C5 fragment) types serve as low
and high energy intermediates for the cobalt ions migration around the C60 cage. Formation of cobalt
dimers can be the final stage of evolution of Con(C60)x atomic structure approaching the equilibrium
atomic geometry. For higher n (3-8) the formation of Ξ·2, Ξ·2 or Ξ·1 coordination bonds between Con
fragment and C60 molecules through carbon hexagons results in stable complex nanoclusters with nonmonotonic
change of average spin momentum upon the number of cobalt atoms in the Con cores. The
theoretical results are compared with corresponding experimental data
Strong Electron Correlations Determine the Stability and Properties of Er-doped Silicon Quantum Dots
Π‘ ΠΏΠΎΠΌΠΎΡΡΡ ΡΠ΅ΠΎΡΠΈΠΈ ΡΡΠ½ΠΊΡΠΈΠΎΠ½Π°Π»Π° ΠΏΠ»ΠΎΡΠ½ΠΎΡΡΠΈ (DFT) Π² ΡΠ°Π±ΠΎΡΠ΅ ΠΏΡΠΎΠ²ΠΎΠ΄ΠΈΠ»ΠΎΡΡ ΠΈΠ·ΡΡΠ΅Π½ΠΈΠ΅ ΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΠΎΠΉ ΡΡΡΡΠΊΡΡΡΡ ΠΊΡΠ΅ΠΌΠ½ΠΈΠ΅Π²ΡΡ
ΠΊΠ²Π°Π½ΡΠΎΠ²ΡΡ
ΡΠΎΡΠ΅ΠΊ ΠΠΎΠ»Π΄Π±Π΅ΡΠ³ΠΎΠ²ΡΠΊΠΎΠ³ΠΎ ΡΠΈΠΏΠ° Ρ ΡΠ΅Π½ΡΡΠ°Π»ΡΠ½ΡΠΌΠΈ ΡΠΈΠΌΠΌΠ΅ΡΡΠΈΡΠ΅ΡΠΊΠΈΠΌΠΈ ΠΏΡΡΡΠΎΡΠ°ΠΌΠΈ ΠΈ ΠΈΡ
ΡΠ½Π΄ΠΎΡΠ΄ΡΠ°Π»ΡΠ½ΡΠΌΠΈ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ°ΠΌΠΈ Ρ ΡΡΠ±ΠΈΠ΅ΠΌ. ΠΠΎΡΠ»Π΅ ΠΎΠΏΡΠΈΠΌΠΈΠ·Π°ΡΠΈΠΈ ΡΡΡΡΠΊΡΡΡΡ Ρ ΠΏΠΎΠΌΠΎΡΡΡ DFT-ΠΌΠ΅ΡΠΎΠ΄Π° Π±ΡΠ» ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½ ΡΠ°ΡΡΠ΅Ρ ΡΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΡΡ
ΡΠ²ΠΎΠΉΡΡΠ² Er-Π΄ΠΎΠΏΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ Π½Π°Π½ΠΎΠΊΡΠΈΡΡΠ°Π»Π»ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΊΡΠ΅ΠΌΠ½ΠΈΡ. ΠΡΠΎΠΌΠ΅ ΡΠΎΠ³ΠΎ, ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΏΠΎΠ·Π²ΠΎΠ»ΠΈΠ»ΠΈ ΠΎΠ±ΡΡΡΠ½ΠΈΡΡ ΡΠΎΠ»Ρ ΡΠΈΠΌΠΌΠ΅ΡΡΠΈΠΈ ΡΠ΅Π½ΡΡΠ°Π»ΡΠ½ΡΡ
ΠΏΡΡΡΠΎΡ Π² ΠΊΠ²Π°Π½ΡΠΎΠ²ΡΡ
ΡΠΎΡΠΊΠ°Ρ
ΠΈ ΠΏΡΠΎΠ²Π΅ΡΡΠΈ ΠΈΠ½ΡΠ΅ΡΠΏΡΠ΅ΡΠ°ΡΠΈΡ ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠ΅ΠΉ Π² ΠΏΠ»ΠΎΡΠ½ΠΎΡΡΡΡ
ΡΠΎΡΡΠΎΡΠ½ΠΈΠΉ.The electronic structure of the Goldberg silicon quantum dots with central symmetric hollows and their endohedral complexes with erbium was studied using DFT with and without the strong electron correlations, whose inclusion was found to determine the binding energy. Based on optimized DFT structures, we were able to explain the details of Er-doped nanocrystalline silicon made in experiment. The role of symmetry of the central hollows in quantum dots was elucidated, and the key features of the density of states are explained, providing information for the tuning and design of Er-doped silicon light emitters
Two-Dimensional Lattices of VN: Emergence of Ferromagnetism and Half-Metallicity on Nanoscale
Two-dimensional
(2D) ferromagnets with high spin-polarization ratio
and high Curie temperature are crucial for developing next-generation
spintronic nanodevices. Using first-principles calculations, we predict
two polymorphic modifications (<i>t</i>-VN and <i>h</i>-VN) of 2D VN lattices that have robust intrinsic ferromagnetic properties
and high Curie temperatures. Whereas <i>t</i>-VN has 99.9%
of spin polarization at the Fermi level, <i>h</i>-VN possesses
a half-metallic type of conductivity and keeps it after contact with
semiconducting MoS<sub>2</sub>, which can be used as the substrate
for <i>h</i>-VN synthesis and valley polarized contacts.
Magnetocrystalline anisotropy energy of 2D VN polymorphs is found
to be at least an order larger than those of Fe and Ni bulks. The
phonon spectra and ab initio molecular dynamic simulation prove that
2D VN lattices have a high thermodynamic stability. These advantages
demonstrate that the VN monolayers should be promising candidates
for low-dimensional spintronic devices
Theoretical Investigation of the Prospect to Tailor ZnO Electronic Properties with VP Thin Films
The atomic and electronic structure of vanadium phosphide one- to four-atomic-layer thin films and their composites with zinc oxide substrate are modelled by means of quantum chemistry. Favorable vanadium phosphide to ZnO orientation is defined and found to remain the same for all the structures under consideration. The electronic structure of the composites is analyzed in detail. The features of the charge and spin density distribution are discussed
Ni-modification of al (III) Surface and use it as Hydrogen Storage Material
Π Π΄Π°Π½Π½ΠΎΠΉ ΡΠ°Π±ΠΎΡΠ΅ ΠΏΡΠΎΠ²ΠΎΠ΄ΠΈΠ»ΠΎΡΡ ΡΠ΅ΠΎΡΠ΅ΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅ Π΄ΠΎΠΏΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠΉ Π½ΠΈΠΊΠ΅Π»Π΅ΠΌ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ
Π°Π»ΡΠΌΠΈΠ½ΠΈΡ, ΠΊΠΎΡΠΎΡΠΎΠ΅ Π±ΡΠ»ΠΎ Π²ΡΠΏΠΎΠ»Π½Π΅Π½ΠΎ Π² ΡΠ°ΠΌΠΊΠ°Ρ
ΡΠ΅ΠΎΡΠΈΠΈ ΡΡΠ½ΠΊΡΠΈΠΎΠ½Π°Π»Π° ΠΏΠ»ΠΎΡΠ½ΠΎΡΡΠΈ (DFT) Ρ
ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ ΠΎΠ±ΠΎΠ±ΡΠ΅Π½Π½ΠΎΠ³ΠΎ Π³ΡΠ°Π΄ΠΈΠ΅Π½ΡΠ½ΠΎΠ³ΠΎ ΠΏΡΠΈΠ±Π»ΠΈΠΆΠ΅Π½ΠΈΡ GGA-PBE. ΠΡΠ»Π° ΠΈΠ·ΡΡΠ΅Π½Π° ΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½Π°Ρ
ΡΡΡΡΠΊΡΡΡΠ° ΠΏΡΠΈ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΠΈ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ Π°Π»ΡΠΌΠΈΠ½ΠΈΡ Ρ Π°ΡΠΎΠΌΠ°ΠΌΠΈ Π½ΠΈΠΊΠ΅Π»Ρ. ΠΡΠΏΠΎΠ»ΡΠ·ΡΡ ΠΌΠ΅ΡΠΎΠ΄
NEB, ΡΠ°ΡΡΡΠΈΡΠ°Π»ΠΈ Π±Π°ΡΡΠ΅Ρ Π΄Π»Ρ Π΄ΠΈΡΡΡΠ·ΠΈΠΈ Π°ΡΠΎΠΌΠ° Π½ΠΈΠΊΠ΅Π»Ρ ΠΏΠΎ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ Π°Π»ΡΠΌΠΈΠ½ΠΈΡ ΠΈ Ρ ΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠΈ
Π² ΠΏΡΠΈΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠ½ΡΠΉ ΡΠ»ΠΎΠΉ. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ Π°ΡΠΎΠΌΠ°ΠΌ Π½ΠΈΠΊΠ΅Π»Ρ ΠΏΡΠ΅Π΄ΠΏΠΎΡΡΠΈΡΠ΅Π»ΡΠ½Π΅Π΅ Π·Π°ΠΌΠ΅ΡΠ°ΡΡ
Π°ΡΠΎΠΌΡ Π°Π»ΡΠΌΠΈΠ½ΠΈΡ Π² ΠΏΡΠΈΠΏΠΎΠ²Π΅ΡΡ
Π½ΠΎΡΡΠ½ΡΡ
ΡΠ»ΠΎΡΡ
, ΡΡΠΎ Π²ΠΏΠΎΡΠ»Π΅Π΄ΡΡΠ²ΠΈΠΈ ΠΏΡΠΈΠ²ΠΎΠ΄ΠΈΡ ΠΊ ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΡ
ΠΈΠ½ΡΠ΅ΡΠΌΠ΅ΡΠ°Π»Π»ΠΈΠ΄Π° Al3Ni. ΠΠ°Π½Π½Π°Ρ ΡΠ°Π·Π° Π±ΡΠ»Π° ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½Π° Π½Π° Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΡ ΡΠΎΡΠ±ΡΠΈΠΈ Π²ΠΎΠ΄ΠΎΡΠΎΠ΄Π°.
Π Π΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΏΠΎΠΊΠ°Π·Π°Π»ΠΈ, ΡΡΠΎ ΠΏΡΠΈ Π½ΠΎΡΠΌΠ°Π»ΡΠ½ΡΡ
ΡΡΠ»ΠΎΠ²ΠΈΡΡ
Π²ΠΎΠ΄ΠΎΡΠΎΠ΄Ρ Π½Π΅ ΡΠ²ΠΎΠΉΡΡΠ²Π΅Π½Π½ΠΎ ΡΠΎΠ΄Π΅ΡΠΆΠ°ΡΡΡΡ
Π² Π΄Π°Π½Π½ΠΎΠΉ ΡΠ°Π·Π΅In this paper, a theoretical study of the nickel -doped of aluminum surface was carried in the framework
of density functional theory (DFT) using the generalized gradient approximation GGA-PBE. The
electronic structure of interface Al(III) surface and nickel atoms was investigated. Using the method of
NEB, the diffusion barrier of the nickel atom from the surface into the subsurface layer was calculated.
It values shows that the nickel atom is preferable to replace aluminum atom in the subsurface layer,
which subsequently leads to the formation of intermetallic Al3Ni. This phase has been investigated the
possibility of hydrogen sorption. The results showed that the hydrogen is not typical contained in this
phase under normal condition
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