Structures and aromaticity of the planar B2XY (X=N, P and Y=O, S, Se) and Al2MN (M=C, Si, Ge and N=S, Se) clusters

Xu, Wen; Zhang, Rui Chun; Lu, Shixiang; Zhang, Yuan Chun

doi:10.1016/j.theochem.2008.09.026

Cited by 12 publications

(6 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…54 A similar TCI property has also been confirmed in the PbTe-SnTe alloy system of Pb 1−x Sn x Te in the inverted-band regime for x ∼ 0.4. 53 In contrast to the TI materials discussed so far, PSS shows a pair of Dirac cones straddling theX point for the (001) surface-state projection [ Fig. 15(b)], instead of a single Dirac cone, which was attributed to the Lifshitz transition as a result of (110) mirror-symmetry-protected topological orders.…”

Section: Bi2se3: Time-reversal-symmetry-protected Topological Insumentioning

confidence: 82%

“…Pb 1−x Sn x Se (PSS) has been proposed as the first example of a TI with crystalline-symmetry-protected topological orders. 49,[52][53][54] The TI state of PSS is attributed to the cubic symmetry of rock-salt type [ Fig. 15(a)] that protects topological orders as a topological crystalline insulator (TCI).…”

Section: Bi2se3: Time-reversal-symmetry-protected Topological Insumentioning

confidence: 99%

See 1 more Smart Citation

Fundamental insights to topological quantum materials: A real-space view of 13 cases by supersymmetry of valence bonds approach

Chou

2019

Applied Physics Reviews

View full text Add to dashboard Cite

We present a real-space view of one-dimensional (1D) to three-dimensional (3D) topological materials with 13 representative samples selected from each class, including 1D trans-polyacetylene, two-dimensional (2D) graphene, and 3D topological insulators, Dirac semimetals, Weyl semimetals, and nodal-line semimetals. This review is not intended to present a complete up-to-date list of publications on topological materials, nor to provide a progress report on the theoretical concepts and experimental advances, but rather to focus on an analysis based on the valence-bond model to help the readers gain a more balanced view of the real-space bonding electron characteristics at the molecular level versus the reciprocal-space band picture of topological materials. Starting from a brief review of low-dimensional magnetism with "toy models" for a 1D Heisenberg antiferromagnetic (HAF) chain, 1D trans-polyacetylene and 2D graphene are found to have similar conjugated π-bond systems, and the Dirac cone is correlated to their unconventional 1D and 2D conduction mechanisms. Strain-driven and symmetry-protected topological insulators are introduced from the perspective of material preparation and valence-electron sharing in the valence-bond model analysis. The valence-bond models for the newly developed Dirac semimetals, Weyl semimetals, and nodal line semimetals are examined with more emphasis on the bond length and electron sharing, which is found consistent with the band picture. The real-space valence-bond analysis of topological materials with a conjugated π-bond system suggests that these topological materials must be classified with concepts borrowed from group theory and topology, so that a supersymmetry may absorb the fluctuating broken symmetry. Restoration of a thermodynamic system with higher entropy (i.e., the lower Gibbs free energy) is more appropriate to describe such topological materials instead of the traditional material classification with the lowest enthalpy for the presumed rigid crystal structure. arXiv:1902.02589v1 [cond-mat.str-el]

show abstract

Section: Bi2se3: Time-reversal-symmetry-protected Topological Insumentioning

confidence: 82%

Section: Bi2se3: Time-reversal-symmetry-protected Topological Insumentioning

confidence: 99%

Fundamental insights to topological quantum materials: A real-space view of 13 cases by supersymmetry of valence bonds approach

Chou

2019

Applied Physics Reviews

View full text Add to dashboard Cite

show abstract

“…Rings with negative and positive NICS values are considered as aromatic and antiaromatic, respectively. Although theoreticians have used the NICS to explain the aromatic/antiaromatic behavior in various organic [35][36][37][38][39] and inorganic compounds, [40][41][42][43][44][45][46] in some cases it is not a reliable indicator and leads to an incorrect prediction of aromaticity. 47 Induced magnetic field 48,49 and first order induced current densities as implemented in the program GIMIC 50 are the other important magnetic indices.…”

Section: Introductionmentioning

confidence: 99%

Shannon entropy as a new measure of aromaticity, Shannon aromaticity

Noorizadeh

Shakerzadeh

2010

Phys. Chem. Chem. Phys.

171

105

View full text Add to dashboard Cite

Based on the local Shannon entropy concept in information theory, a new measure of aromaticity is introduced. This index, which describes the probability of electronic charge distribution between atoms in a given ring, is called Shannon aromaticity (SA). Using B3LYP method and different basis sets (6-31G**, 6-31+G** and 6-311++G**), the SA values of some five-membered heterocycles, C(4)H(4)X, are calculated. Significant linear correlations are observed between the evaluated SAs and some other criteria of aromaticity such as ASE, Lambda and NICS indices. According to the obtained relationships, the range of 0.003 < SA < 0.005 is chosen as the boundary of aromaticity/antiaromaticity. Using B3LYP/6-31+G** level of theory, the Shannon aromaticities for a series of mono-substituted benzene derivatives are calculated and analyzed. It is found that the least standard deviation between the aromaticities and the best linear correlation with the Hammett substituent constants are observed for the new index in comparison with the other indices. Also the values of the new index are evaluated for some substituted penta- and heptafulvenes, which successfully predict the order of aromaticity in these compounds. Applying this index to some non-benzonoids, linear and angular polyacenes also give satisfactory results and prove to be quite suitable for determining the local aromaticity of different rings in polyaromatic hydrocarbons.

show abstract

“…The XRD patterns of CaAl-PO 4 -LDHs synthesized after crystallization reactions are shown in Figure 1. The main characteristic peaks of CaAl-PO 4 -LDHs display sharp and intense (003), (006), ( 110) and (203) reflections corresponding to PDF#50-0652, which indicates that the prepared samples had a typical hydrotalcite lamellar structure [21]. The shifts in the diffraction peaks towards lower angles indicate that PO 4 3− was successfully inter-calated into the interlayer spacing of calcium-aluminum hydrotalcites [14].…”

Section: Xrd Analysis Of Caal-po 4 -Ldhs Synthesized Via Different Pr...mentioning

confidence: 97%

Preparation of PO43−-Intercalated Calcium–Aluminum Hydrotalcites via Coprecipitation Method and Its Flame-Retardant Effect on Bamboo Scrimber

Ran

Yang

et al. 2023

Molecules

View full text Add to dashboard Cite

To improve the flame retardancy of bamboo scrimber, flame-retardant CaAl-PO4-LDHs were synthesized via the coprecipitation method using PO43− as the anion of an intercalated calcium–aluminum hydrotalcite in this work. The fine CaAl-PO4-LDHs were characterized via X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), cold field scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and thermogravimetry (TG). Different concentrations (1% and 2%) of CaAl-PO4-LDHs were used as flame retardants for the bamboo scrimber, and the flame retardancy of the bamboo scrimber was characterized via cone calorimetry. The results showed that CaAl-PO4-LDHs with excellent structures were successfully synthesized via the coprecipitation method in 6 h and at 120 °C. Compared with the bamboo scrimber without the flame retardant treatment, the peak heat release rate (HRR) of the bamboo scrimber treated with 1% and 2% concentrations of flame-retardant CaAl-PO4-LDHs decreased by 16.62% and 34.46%, the time taken to reach the exothermic peak was delayed by 103 s and 204 s and the Time to Ignition (TTI) was increased by 30% and 40%, respectively. Furthermore, the residual carbon of the bamboo scrimber did not change significantly, increasing by 0.8% and 2.08%, respectively. CO production decreased by 18.87% and 26.42%, respectively, and CO2 production decreased by 11.11% and 14.46%, respectively. The combined results show that the CaAl-PO4-LDHs synthesized in this work significantly improved the flame retardancy of bamboo scrimber. This work exhibited the great potential of the CaAl-PO4-LDHs, which were successfully synthesized via the coprecipitation method and applied as a flame retardant to improve the fire safety of bamboo scrimber.

show abstract

Structures and aromaticity of the planar B2XY (X=N, P and Y=O, S, Se) and Al2MN (M=C, Si, Ge and N=S, Se) clusters

Cited by 12 publications

References 44 publications

Fundamental insights to topological quantum materials: A real-space view of 13 cases by supersymmetry of valence bonds approach

Fundamental insights to topological quantum materials: A real-space view of 13 cases by supersymmetry of valence bonds approach

Shannon entropy as a new measure of aromaticity, Shannon aromaticity

Preparation of PO43−-Intercalated Calcium–Aluminum Hydrotalcites via Coprecipitation Method and Its Flame-Retardant Effect on Bamboo Scrimber

Contact Info

Product

Resources

About