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Title: Orientational Glass Formation in Substituted Hybrid Perovskites

Authors:
ORCiD logo [1];  [1];  [2];  [2]; ORCiD logo [3];  [2]; ORCiD logo [1]
  1. Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
  2. Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
  3. Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States; Forschunqszeutrum Juelich GmbH, JCNS at SNS, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6475, United States
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1417396
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 29; Journal Issue: 23
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Mozur, Eve M., Maughan, Annalise E., Cheng, Yongqiang, Huq, Ashfia, Jalarvo, Niina, Daemen, Luke L., and Neilson, James R. Orientational Glass Formation in Substituted Hybrid Perovskites. United States: N. p., 2017. Web. doi:10.1021/acs.chemmater.7b04017.
Mozur, Eve M., Maughan, Annalise E., Cheng, Yongqiang, Huq, Ashfia, Jalarvo, Niina, Daemen, Luke L., & Neilson, James R. Orientational Glass Formation in Substituted Hybrid Perovskites. United States. doi:10.1021/acs.chemmater.7b04017.
Mozur, Eve M., Maughan, Annalise E., Cheng, Yongqiang, Huq, Ashfia, Jalarvo, Niina, Daemen, Luke L., and Neilson, James R. 2017. "Orientational Glass Formation in Substituted Hybrid Perovskites". United States. doi:10.1021/acs.chemmater.7b04017.
@article{osti_1417396,
title = {Orientational Glass Formation in Substituted Hybrid Perovskites},
author = {Mozur, Eve M. and Maughan, Annalise E. and Cheng, Yongqiang and Huq, Ashfia and Jalarvo, Niina and Daemen, Luke L. and Neilson, James R.},
abstractNote = {},
doi = {10.1021/acs.chemmater.7b04017},
journal = {Chemistry of Materials},
number = 23,
volume = 29,
place = {United States},
year = 2017,
month =
}
  • Hybrid organic-inorganic perovskites have gained notoriety in the photovoltaic community for their composition-tunable band gaps and long-lived electronic excited states, which are known to be related to the crystalline phase. While indirect evidence suggests that coupling between polar organic cations affects the phase behavior, it remains unclear how the coupling manifests in hybrid perovskites such as methylammonium lead halides (CH 3NH 3PbX 3). Here, we present crystallographic and spectroscopic data for the series (CH 3NH 3) 1-xCs xPbBr 3. CH 3NH 3PbBr 3 behaves as a plastic crystal in the high temperature cubic phase, and substitution of CH 3NH 3more » + with Cs + leads to the formation of an orientational glass. While the organic molecule exhibits slow, glassy reorientational dynamics, the inorganic framework continues to undergo crystallographic phase transitions. These crystallographic transitions occur in the absence of thermodynamic signatures in the specific heat, which suggests that the phase transitions result from underlying instabilities intrinsic to the inorganic lattice. However, these transitions are not decoupled from the reorientations of the organic molecule, as indicated by inelastic and quasielastic neutron scattering. Observation of a reentrant phase transition in (CH 3NH 3) 0.8Cs 0.2PbBr 3 permits the resolution of these complex behaviors within the context of strain mediated interactions. Lastly, together, these results provide critical insight into the coupled phase behavior and dynamics in hybrid perovskites.« less
  • The microscopic model for two-dimensional distribution function [ital P]([sigma],[eta]) for quadrupolar glass freezing of axial ([sigma]) and eccentric ([eta]) order parameters in solid hydrogen is considered within the Sherrington-Kirkpatrick mean-field approach. Assuming the exchange interactions between axial and eccentric quadrupoles to be independent Gaussian random variables with variance [ital J][sup 2]/[ital N] and [ital K][sup 2]/[ital N], respectively (with [ital N] being the number of lattice sites), we derived a set of self-consistent equations for quadrupolar order parameters and the corresponding local susceptibilities. While for [ital J][ne][ital K] the axial quadrupolar order parameter is nonvanishing in the high-temperature phase duemore » to broken local symmetry and the corresponding quadrupolar susceptibility exhibits smeared-out behavior, the eccentric order parameter becomes zero at well-defined critical temperature depending on the ratio [ital K]/[ital J]. Furthermore, the properties of the [ital P]([sigma],[eta]) distribution function are investigated by introducing a single effective order parameter [sigma][sub [ital e][ital f][ital f]] (1[lt][sigma][sub [ital e][ital f][ital f]][lt]0) directly related to the second frequency moment of the nuclear magnetic resonance line shapes. Comparison of the present microscopic theory with earlier phenomenological approaches to the problem is also made.« less
  • It has been shown that in the above-mentioned paper the author starts from the orientational Hamiltonian of solid hydrogen containing an unphysical term leading, in general, to the nonvanishing average dipolar momentum of hydrogen molecules.
  • The mean-field theory of the quadrupolar glass (QG) is presented using a microscopic approach. It is shown that the reaction-polarization effects caused by short-range spatial correlations are well distinguished from those of random-bond spin glasses. They control the QG concentration threshold and result in an incomplete orientational order. The QG ground state (zero quadrupolization, unsaturated Edwards-Anderson-type orientational order parameter) is predicted. Thermodynamic characteristics, namely entropy, pressure and free energy as well as the related heat capacity and Gruneisen parameter are estimated. The ground-state findings (incomplete order, residual entropy) are similar to those of short-range Potts glasses. A correspondence between densitymore » matrix and mean field treatment to the QG problem is also discussed.« less
  • A comparative analysis of experimental data on the orientational order parameter, heat capacity and Gruneisen parameter with those predicted by the mean-field microscopic theory given in the accompanying paper is carried out. The orientation-motion freezing mechanisms driven by the strain, quadrupolar and reaction fields are identified. It is proved that within the quadrupolar glass (QG) phase the random-site effects dominate over random-bond dilution effects. The entry to the QG phase is characterized by the freezing temperature, at which the total intrinsic field disappears. The QG ground-state distribution function known from NMR spectroscopy is proposed.