scholarly journals Metal cation s lone-pairs increase octahedral tilting instabilities in halide perovskites

2021 ◽  
Author(s):  
Lingyuan Gao ◽  
Lena Yadgarov ◽  
Rituraj Sharma ◽  
Roman Korobko ◽  
Kyle M. McCall ◽  
...  
Keyword(s):  
Metal Cation ◽  
Lone Pair ◽  
Lone Pairs ◽  
Halide Perovskites ◽  
Octahedral Tilting ◽  
Structural Instabilities

Lone-pair covalency can faciliate dynamic tilting of MBr6 octahedra and increase dynamic structural instabilities.

scholarly journals Strongly Anharmonic Octahedral Tilting in Two-Dimensional Hybrid Halide Perovskites

ACS Nano ◽  
2021 ◽  
Author(s):  
Matan Menahem ◽  
Zhenbang Dai ◽  
Sigalit Aharon ◽  
Rituraj Sharma ◽  
Maor Asher ◽  
...  
Keyword(s):  
Two Dimensional ◽  
Halide Perovskites ◽  
Octahedral Tilting

Theoretical perspective of the lone pair activity influence on band gap and SHG response of lead borates

RSC Advances ◽  
2015 ◽  
Vol 5 (97) ◽  
pp. 79882-79887 ◽  
Author(s):  
Danni Li ◽  
Qun Jing ◽  
Chen Lei ◽  
Shilie Pan ◽  
Bingbing Zhang ◽  
...  
Keyword(s):  
Band Gap ◽  
Theoretical Perspective ◽  
Lone Pair ◽  
Red Shift ◽  
Lone Pairs

Metal lone pairs play an important role in determining the SHG enhancement and bandgap red shift.

Anomalous stabilizing and destabilizing effects in some cyclic π-electron systems

1993 ◽  
Vol 71 (8) ◽  
pp. 1123-1127 ◽  
Author(s):  
Peter Politzer ◽  
M. Edward Grice ◽  
Jane S. Murray ◽  
Jorge M. Seminario
Keyword(s):  
Ab Initio ◽  
Lone Pair ◽  
Electrostatic Potentials ◽  
Electron Delocalization ◽  
Isodesmic Reaction ◽  
Computational Studies ◽  
Electron Systems ◽  
Molecular Electrostatic Potentials ◽  
Lone Pairs

Ab initio computational studies have been carried out for three molecules that are commonly classed as antiaromatic: cyclobutadiene (1), 1,3-diazacyclobutadiene (7), and 1,4-dihydropyrazine (6). Their dinitro and diamino derivatives were also investigated. Stabilizing or destabilizing energetic effects were quantified by means of the isodesmic reaction procedure at the MP2/6-31G*//HF/3-21G level, and calculated molecular electrostatic potentials (HF/STO-5G//HF/3-21G) were used as a probe of electron delocalization. Our results do not show extensive delocalization in the π systems of any one of the three parent molecules. The destabilization found for 1 and 7 is attributed primarily to strain and to repulsion between the localized π electrons in the C=C and C=N bonds, respectively. However, 6 is significantly stabilized, presumably due to limited delocalization of the nitrogen lone pairs. NH2 groups are highly stabilizing, apparently because of lone pair delocalization. NO2 is neither uniformly stabilizing nor destabilizing.

scholarly journals Expression and interactions of stereochemically active lone pairs and their relation to structural distortions and thermal conductivity

IUCrJ ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 480-489 ◽  
Author(s):  
Kasper Tolborg ◽  
Carlo Gatti ◽  
Bo B. Iversen
Keyword(s):  
Thermal Conductivity ◽  
Density Functional ◽  
Lone Pair ◽  
Density Functional Theory Calculations ◽  
Orbital Interaction ◽  
Void Space ◽  
Metal Compounds ◽  
Bond Angles ◽  
Lone Pairs ◽  
Bonding Effect

In chemistry, stereochemically active lone pairs are typically described as an important non-bonding effect, and recent interest has centred on understanding the derived effect of lone pair expression on physical properties such as thermal conductivity. To manipulate such properties, it is essential to understand the conditions that lead to lone pair expression and provide a quantitative chemical description of their identity to allow comparison between systems. Here, density functional theory calculations are used first to establish the presence of stereochemically active lone pairs on antimony in the archetypical chalcogenide MnSb2O4. The lone pairs are formed through a similar mechanism to those in binary post-transition metal compounds in an oxidation state of two less than their main group number [e.g. Pb(II) and Sb(III)], where the degree of orbital interaction (covalency) determines the expression of the lone pair. In MnSb2O4 the Sb lone pairs interact through a void space in the crystal structure, and their their mutual repulsion is minimized by introducing a deflection angle. This angle increases significantly with decreasing Sb—Sb distance introduced by simulating high pressure, thus showing the highly destabilizing nature of the lone pair interactions. Analysis of the chemical bonding in MnSb2O4 shows that it is dominated by polar covalent interactions with significant contributions both from charge accumulation in the bonding regions and from charge transfer. A database search of related ternary chalcogenide structures shows that, for structures with a lone pair (SbX 3 units), the degree of lone pair expression is largely determined by whether the antimony–chalcogen units are connected or not, suggesting a cooperative effect. Isolated SbX 3 units have larger X—Sb—X bond angles and therefore weaker lone pair expression than connected units. Since increased lone pair expression is equivalent to an increased orbital interaction (covalent bonding), which typically leads to increased heat conduction, this can explain the previously established correlation between larger bond angles and lower thermal conductivity. Thus, it appears that for these chalcogenides, lone pair expression and thermal conductivity may be related through the degree of covalency of the system.

scholarly journals The underappreciated lone pair in halide perovskites underpins their unusual properties

MRS Bulletin ◽  
2020 ◽  
Vol 45 (6) ◽  
pp. 467-477 ◽  
Author(s):  
Douglas H. Fabini ◽  
Ram Seshadri ◽  
Mercouri G. Kanatzidis
Keyword(s):  
Lone Pair ◽  
Halide Perovskites ◽  
Image Position

Abstract

Rabbit ears concepts of water lone pairs: a reply to comments of Hiberty, Danovich, and Shaik

2015 ◽  
Vol 16 (3) ◽  
pp. 694-696 ◽  
Author(s):  
A. D. Clauss ◽  
M. Ayoub ◽  
J. W. Moore ◽  
C. R. Landis ◽  
F. Weinhold
Keyword(s):  
Lone Pair ◽  
Lone Pairs ◽  
Rabbit Ears

We respond to recent comments (Hibertyet al., 2015) on our earlier article (Clausset al., 2014) concerning “rabbit ears” depictions of lone pair orbitals in water and other species.

scholarly journals Correlating structure and electronic band-edge properties in organolead halide perovskites nanoparticles

2016 ◽  
Vol 18 (22) ◽  
pp. 14933-14940 ◽  
Author(s):  
Qiushi Zhu ◽  
Kaibo Zheng ◽  
Mohamed Abdellah ◽  
Alexander Generalov ◽  
Dörthe Haase ◽  
...  
Keyword(s):  
Lattice Strain ◽  
Lone Pair ◽  
Band Edge ◽  
Electronic Band ◽  
Halide Perovskites ◽  
Organolead Halide ◽  
Stereochemical Activity

Lattice strain modifies the subtle stereochemical activity of the Pb2+ lone-pair in organolead halide perovskites (OHLP) nanoparticles.

Protonation and microwave-assisted heating induced excitation of lone-pair electrons in graphitic carbon nitride for increased photocatalytic hydrogen generation

2019 ◽  
Vol 7 (35) ◽  
pp. 20223-20228 ◽  
Author(s):  
Dandan Wu ◽  
Shaonian Hu ◽  
Hongyun Xue ◽  
Xiaojuan Hou ◽  
Haiwei Du ◽  
...  
Keyword(s):  
Carbon Nitride ◽  
Hydrogen Generation ◽  
Lone Pair ◽  
Graphitic Carbon ◽  
Graphitic Carbon Nitride ◽  
Microwave Assisted ◽  
Photocatalytic Hydrogen Generation ◽  
Lone Pairs ◽  
Lone Pair Electrons ◽  
Generation Activity

Graphitic carbon nitride (g-C3N4) with pronounced excitation of lone pairs enhances its photocatalytic hydrogen (H2) generation activity.

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