Determination of the I2 bond-length distribution in liquid, solid and solution, by extended x-ray absorption fine structure spectroscopy

Buontempo, U.; Cicco, Andrea Di; Filipponi, A.; Nardone, M.; Postorino, P.

doi:10.1063/1.3396311

Cited by 17 publications

(16 citation statements)

References 27 publications

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“…A time-dependent radial distribution function of I−I bond distances (see SI animated movie), shows a peak transition, shortly after 200 fs, toward an I 2 bond length of 2.7 Å. 63 Previous studies regarding I 2 formation in relation to MAPbI 3 defects have been established. 64,65 However, in previous work, I 2 formation is discussed as an interstitial I defect rather than the V Pb presented here.…”

Section: Resultsmentioning

confidence: 90%

Role of Lead Vacancies for Optoelectronic Properties of Lead-Halide Perovskites

2017

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Methylammonium lead iodide perovskite materials have been shown to be efficient in photovoltaic devices. The current fabrication process has not been perfected, leaving defects such as site vacancies, which can trap charge and have a detrimental effect on photogenerated charge carriers. Here focus is placed on the effect a Pb site vacancy has on the charge-carrier dynamics following photoexcitation. The electronic structure of materials with vacancies is often found in open-shell configurations with unpaired electrons in the conduction/valence bands To accurately describe unpaired electrons, spin-polarized and noncollinear spin calculations are performed on both neutral and charged vacancy systems. This work presents spin-polarized and noncollinear spin ground-state electronic structures and nonradiative rates of charge-carrier relaxation and introduces an extension to a novel procedure to compute photoluminescence spectra for open-shell models. This study describes nonadiabatic dynamics of MAPbI3 models within a Redfield formalism focusing on the role of a Pb vacancy defect on electronic relaxation processes. Results show the vacancy of the Pb ion introducing a new energy state within the unblemished material band gap region. This additional unoccupied state is expected to increase the nonradiative relaxation lifetime of the excited electron, allowing for a longer lifetime of the charge carrier and increased opportunity for secondary relaxation mechanisms or collection to take place.

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Section: Resultsmentioning

confidence: 90%

Role of Lead Vacancies for Optoelectronic Properties of Lead-Halide Perovskites

2017

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“…The I-Pb-I layer is approximately 0.7 nm think, the distance between I atoms in neighboring sandwiches is 0.42 nm and distance between I-I planes in different sandwiches is 0.35 nm. As a reference, the I-I distance in gaseous I2 is 0.27 nm [36].…”

Section: The Basic Structure Of Pbi2mentioning

confidence: 99%

A review of polytypism in lead iodide

Beckmann

2010

Cryst. Res. Technol.

107

109

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Key words lead iodide structure, layered inorganic structures, viewing different polytypes Lead Iodide (PbI2) is an important inorganic solid for both basic scientific research and possible technological applications and in this brief review we discuss the structure of PbI2. Although the basic structure is a simple I-Pb-I layered structure with a [PbI6] 4-near-octahedron being the basic building block, there are many ways of stacking the layers which results in many polytypes. We present 20 of the 23 entries for the structure of PbI2 from the Inorganic Structural Database and order them by polytype. This represents more than 80 years of crystallographic research in the structure of this compound. We present a simple way to view the 2H, 4H, 6H, and 6R polytypes and extend the procedure to higher-order polytypes. We note a relationship, not generally appreciated, between the distortion of the near [PbI6] 4-octahedrons and the polytype. We suggest that the significance of vacancies has only recently been appreciated. We suggest that small discrepancies in structure determination are probably due to different distributions of vacancies and that there are, in practice, very many structures for macroscopic or even mesoscopic samples of a given polytype when vacancies are considered.

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“…Hypervalent bonding (more specifically: 3c-4e bonding) in I3 -, formally derived from donation of a lone pair on Iinto the * 320 of normal-valent I2. I-I distances for free I2,20 and symmetrical I3 -(decamethylferrocenium salt)21 are also shown, as well as heuristic bond orders (B.O. ).…”

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confidence: 96%

Covalent d-Block Organometallics: Teaching Lewis Structures and sd/sd2 Hybridization Gives Students Additional Explanations and Powerful Predictive Tools

Fekl

2021

Preprint

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Despite tremendous efforts by instructors and textbook authors, students find it difficult to develop useful chemical intuitions about preferred structures, structural trends, and properties of even the most common d-block element organometallic species, that is d6, d8, and d10 systems. A full molecular orbital analysis of a transition metal species is not always feasible or desirable, and crystal field theory, while generally useful, is often too simplistic and limited. It would be helpful to give students of organometallic chemistry an additional toolkit that helps them to understand d-block compounds, in particular highly covalent ones. It is well known in the research literature in organometallic chemistry that hybridization arguments involving s and d orbitals (such as sd and sd2 hybridization for d8 and d6 systems, respectively) provides useful insight. However, this knowledge is much underused in undergraduate teaching and not taught in undergraduate textbooks. The purpose of this article is to make descriptions of bonding that are based on s,d-hybridized orbitals more accessible in a way that is directly useful for undergraduate teaching. Geometries of unusual low-coordinate structures can be successfully predicted. An in-depth physical explanation for the trans-influence, the weakening of a bond due to a strong bond trans to it, is provided. A clear explanation is given for why the cis isomer normally more stable than the trans isomer in square-planar d8 complexes of the type MR2L2 (R = alkyl/aryl, L = relatively weakly bonded neutral ligand). Similarly, the relative stability of fac versus mer isomers in octahedral d6 complexes of the type MR3L3 is explained. Relevant to catalysis, the method explains why strongly donating ligands do not always facilitate oxidative addition and why 12-electron and 14-electron Pd(0) species are thermodynamically much more accessible than one might expect. The method capitalizes on 1st year knowledge such as the ability to write Lewis structures and to use hybridization arguments. It also ties into the upper-year experience, including graduate school, where covalent d-block complexes may be encountered in research and where the hybridization schemes described here naturally emerge from using the NBO formalism. It is discussed where the method might fit into the inorganic curriculum.<br>

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Determination of the I2 bond-length distribution in liquid, solid and solution, by extended x-ray absorption fine structure spectroscopy

Cited by 17 publications

References 27 publications

Role of Lead Vacancies for Optoelectronic Properties of Lead-Halide Perovskites

Role of Lead Vacancies for Optoelectronic Properties of Lead-Halide Perovskites

A review of polytypism in lead iodide

Covalent d-Block Organometallics: Teaching Lewis Structures and sd/sd2 Hybridization Gives Students Additional Explanations and Powerful Predictive Tools

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