Verbindungen im System BCSi bzw. BSi

Lipp, A.; Röder, Marc

doi:10.1002/zaac.19663440502

Cited by 30 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our bulk calculations give the lattice constants of a = 3.067Å, c = 3.515Å, which are in good agreement with experimental and other theoretical results [5,13]. We used this bulk geometry as the initial geometry for the surface optimizations.…”

supporting

confidence: 83%

First-principles study ofMgB2(0001) surfaces

Yang

Hou

et al. 2002

Phys. Rev. B

View full text Add to dashboard Cite

We report self-consistent ab initio calculations of structural and electronic properties for the B-and Mg-terminated MgB2 (0001) surfaces. We employ ultra-soft pseudopotentials and plane wave basis sets within the generalized gradient approximation. The surface relaxations are found to be small for both B-and Mg-terminated surfaces. For the B-terminated surface, both B σ and π surface bands appear, while only one B π surface band exists near the Fermi level for the Mgterminated surface. The superconductivity of the MgB2 surfaces is discussed. The work function is predicted to be 5.95 and 4.25 eV for the B-and Mg-terminated surfaces respectively. The simulated scanning tunneling microscopy images of the surfaces are not sensitive to the sign and value of the bias voltages, but depend strongly on the tip-sample distance. An image reversal is predicted for the Mg-terminated surface.The surprising discovery [1] of superconductivity at 39K in MgB 2 has attracted great scientific interest. The isotope effect experiments [2,3] indicate that MgB 2 may be a BCS phonon-mediated superconductor, with Tc above the commonly accepted limits for phononassisted superconductivity. Band structure calculations [4,5] show that the Mg donates substantially its 3s electrons to the B layer, and that the Fermi surface is derived mainly from B orbitals with two-dimensional character. The superconductivity is believed to be due to the strong coupling of the holes of the B σ bands to the in-plane B phonon lattice vibrations (E 2g modes) [4].Being a simple, low-cost and high-performance binary intermetallic compound, MgB 2 is a very promising candidate for superconducting device as well as large-scale applications. Experimentally, scanning tunneling spectroscopy measurements of the surface of superconducting MgB 2 have been reported [6,7], and the high-quality caxis-oriented epitaxial MgB 2 thin films have been grown successfully on Al 2 O 3 substrates by using a pulsed laser deposition technique [8]. However, there has not been a theoretical study for the MgB 2 surfaces so far. In this Letter, we report a first-principles study of MgB 2 (0001) surfaces. Both B-and Mg-terminated surfaces are investigated. We show that while the relaxations of the * Corresponding author. E-mail: jlyang@ustc.edu.cn surface layers are small for both surfaces, their electronic structures are quite different.Our calculations were carried out within the generalized gradient approximation (GGA) [9] using ultrasoft pseudopotentials and plane wave basis sets [10,11]. A 1 × 1 × 15 supercell geometry was used to model the surfaces in which there are 15 atomic layers and 15 layers of vacuum (hereafter, 15-layer slab model) . The plane wave cutoff is 257.2 eV for structural optimizations and 321.5 eV for static electronic structure calculations. Brillouin zone integrations were performed on a grid of 13 × 13 × 1 Monkhorst-Pack [12] special points. During the structural optimizations, we fixed the central 3 atomic layers in the bulk configuration and allowed all other at...

show abstract

supporting

confidence: 83%

First-principles study ofMgB2(0001) surfaces

Yang

Hou

et al. 2002

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…Shaffer [32] reported that well formed SiC crystals have a boron solubility limit of 0.1-0.15 wt.% and less perfectly formed crystal show boron concentrations above 0.2 wt.%. The maximum solubility of Si in B 4 C at 2323 K was found to be 2.5 at.% [34]. This was later confirmed by Werheit et al [35] using optical absorption spectrum.…”

Section: The B-c-si Ternary Systemmentioning

confidence: 71%

Thermodynamic assessment of the B–C–Si system

Chen¹,

Qi²,

Zheng³

et al. 2009

Journal of Alloys and Compounds

View full text Add to dashboard Cite

“…The significant enlargement observed for the c axis is consistent with the occupation of the 6 c site by Li + . In the case of the incorporation of Al or Si atoms into the framework of α‐rhombohedral boron the expansion of the unit cell is mainly due to an enlargement of the a axis, thus indicating a different type of substitution …”

Section: Resultsmentioning

confidence: 99%

“…One way to shed light on the bonding situation in boron carbide is the incorporation of additional elements, aiming at a situation with an electron‐precise structure and a large bandgap. About 50 years ago there were reports on boron carbide with additional aluminum or silicon atoms, resulting in rhombohedral structures with slightly enlarged lattice parameters, but no details on the structures were given. Furthermore, the color of crystals was described as black.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Li‐containing Boron Carbide r‐Li_~1B₁₃C₂

Hillebrecht

Vojteer

Sagawe

et al. 2018

Zeitschrift anorg allge chemie

View full text Add to dashboard Cite

Transparent and nearly colorless single crystals of r-LiB 13 C 2 were obtained by reaction of boron with Li 2 CO 3 in a Cu melt at 1250-1300°C. The structure analysis [R3m, a = 5.6535(1), c = 12.5320(2) Å, 421 independent reflections, 22 parameters, R 1 = 0.034, wR 2 = 0.093] revealed a crystal structure that can be described as a filling variant of rhombohedral B 13 C 2 . Li + is located in a void above or below the linear CBC unit. The site occupation is close to 50 % resulting in an electron-precise composition according to Wade's rules if a positive charge is given to the CBC entity: Li + (B 12 ) 2-(CBC) + . The displacement parameters of the CBC unit indicate disorder in the [001] ARTICLE Results and Discussion Crystal StructureSingle crystals of r-LiB 13 C 2 can be selected from other products like Li 2 B 12 C 2 and o-LiB 13 C 2 based on their shape (Figure 1). Li 2 B 12 C 2 forms well-developed rods or bricks, and o-LiB 13 C 2 was obtained as less or more regular hexagonal platelets. In contrast to this, the shapes of crystals of r-LiB 13 C 2 are very irregular. Powdered samples of r-LiB 13 C 2 are of lightgreen color. Interestingly, r-LiB 13 C 2 is only formed if Li 2 CO 3 is used as starting material, being a source for both lithium and carbon. In contrast to this, o-LiB 13 C 2 and the more stable Li 2 B 12 C 2 were obtained from syntheses with elemental Li and C and Sn as an auxiliary metal. [3]

show abstract

Verbindungen im System BCSi bzw. BSi

Cited by 30 publications

References 12 publications

First-principles study ofMgB2(0001) surfaces

First-principles study ofMgB2(0001) surfaces

Thermodynamic assessment of the B–C–Si system

Synthesis and Characterization of Li‐containing Boron Carbide r‐Li_~1B₁₃C₂

Contact Info

Product

Resources

About

Verbindungen im System BCSi bzw. BSi

Cited by 30 publications

References 12 publications

First-principles study ofMgB2(0001) surfaces

First-principles study ofMgB2(0001) surfaces

Thermodynamic assessment of the B–C–Si system

Synthesis and Characterization of Li‐containing Boron Carbide r‐Li~1B13C2

Contact Info

Product

Resources

About

Synthesis and Characterization of Li‐containing Boron Carbide r‐Li_~1B₁₃C₂