skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Exploring Proton Pair Motion Away from the Global Proton–Tuple Energy Minimum in Yttrium-Doped Barium Zirconate
Yttrium-doped barium zirconate is one of the fastest solid-state proton conductors. While previous studies suggest that proton–tuples move as pairs in yttrium-doped barium zirconate, a systematic catalog of possible close proton–tuple moves is missing. Such a catalog is essential to simulating dual proton conduction effects. Density functional theory with the Perdew–Burke–Ernzerhof functional is utilized to obtain the total electronic energy for each proton–tuple. The conjugate gradient and nudged elastic band methods are used to find the minima and transition states for proton–tuple motion. In the lowest-energy configuration, protons are in close proximity to each other and the dopant, significantly affecting the backbone structure. The map of moves away from the global minimum proton–tuple shows that the most critical move for long-range proton conduction is a rotation with a barrier range of 0.31–0.41 eV when the two protons are in close proximity.  more » « less
Award ID(s):
2018427 2320718
PAR ID:
10487801
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
MDPI
Date Published:
Journal Name:
Inorganics
Volume:
11
Issue:
4
ISSN:
2304-6740
Page Range / eLocation ID:
160
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Communications Physics)
    null (Ed.)
    Abstract Proton conduction is an important property for fuel cell electrolytes. The search for molecular details on proton transport is an ongoing quest. Here, we show that in hydrated yttrium doped barium zirconate using X-ray and neutron diffraction that protons tend to localize near the dopant yttrium as a conjugated superstructure. The proton jump time measured using quasi-elastic neutron scattering follows the Holstein-Samgin polaron model, revealing that proton hopping is weakly coupled to the high-frequency O-H stretching motion, but strongly coupled to low-frequency lattice phonons. The ratio of the proton polaron effective mass, m * , and the proton mass is m * / m  = 2, when coupled to the Zr-O stretching mode, giving experimental evidence of proton pairing in perovskites, as a result of proton-phonon coupling. Possible pathways of a proton pair are provided through Nudge Elastic Band calculations. The pairing of protons, when jumping, is discussed in context of a cooperative protonic charge transport process. 
    more » « less
  2. ; ; ; (, MRS Communications)
    Abstract Material changes in yttrium-doped barium zirconate, BaZr 0.8 Y 0.2 O 3– x , were studied using in situ Raman spectroscopy and ex situ x-ray photoelectron spectroscopy analysis. During in situ Raman analysis, samples were heated to temperatures of 300–600 °C and exposed to both dry and humidified H 2 atmospheres. At the lower temperatures (300–450 °C), a new vibrational peak appears in the Raman spectra during exposure to humidified H 2 . The appearance of this feature is reversible, dependent on previous sample history, and possibly results from new, secondary phase formation or lattice distortion. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ; et al (, Journal of Physics D: Applied Physics)
    Abstract Films of α-Ga2O3 (Sn) grown by Halide Vapor Phase Epitaxy (HVPE) on sapphire with starting net donor densities in the range 5×1015- 8.4×1019 cm-3 were irradiated at room temperature with 1.1 MeV protons to fluences from 1013 -1016 cm-2. For the lowest doped samples, the carrier removal rate was ~35 cm-1 at 1014 cm-2 and ~1.3 cm-1 for 1015 cm-2 proton fluence. The observed removal rate could be accounted for by the introduction of deep acceptors with optical ionization energies of 2 eV, 2.8 eV and 3.1 eV. For doped samples doped at 4x1018 cm-3, the initial electron removal rate was 5×103 cm-1 for 1015 cm-2 proton fluence and ~300 cm-1 for 1016 cm-2 proton fluence. The same deep acceptors were observed in photocapacitance spectra, but their introduction rate was orders of magnitude lower than the carrier removal rate. For the heaviest doped samples, an electron removal rate could be measured only after irradiation with the highest proton fluence of 1016 cm-2 and was close to that measured for the 4×1018 cm-3 sample after exposure to the same fluence. Possible reasons for the observed behavior are discussed and radiation tolerances of lightly doped α-Ga2O3 films is higher than for similarly doped β-Ga2O3 layers. 
    more » « less
  4. ; ; ; ; ; ; ; ; (, Biochimica et Biophysica Acta (BBA) - Bioenergetics)
    The aerobic electron transfer chain builds a proton gradient by proton coupled electron transfer reactions through a series of proteins. Complex I is the 昀椀rst enzyme in the sequence. Here transfer of two electrons from NADH to quinone yields four protons pumped from the membrane N- (negative, higher pH) side to the P- (positive, lower pH) side. Protons move through three linear antiporter paths, with a few amino acids and waters providing the route; and through the E-channel, a complex of competing paths, with clusters of interconnected protonatable residues. Proton loading sites (PLS) transiently bind protons as they are transported from N- to P-compartments. PLS can be individual residues or extended clusters of residues. The program MCCE uses Monte Carlos sampling to analyze the E-channel proton binding in equilibrium with individual Molecular Dynamics snapshots from tra- jectories of Thermus thermuphillus Complex I in the apo, quinone and quinol bound states. At pH 7, the 昀椀ve E- channel subunits (Nqo4, Nqo7, Nqo8, Nqo10, and Nqo11) take >25,000 protonation microstates, each with different residues protonated. The microstate explosion is tamed by analyzing interconnected clusters of residues along the proton transfer paths. A proton is bound and released from a cluster of 昀椀ve coupled residues on the protein N-side and to six coupled residues in the protein center. Loaded microstates bind protons to sites closer to the P-side in the forward pumping direction. MCCE microstate analysis identi昀椀es strongly coupled proton binding amongst individual residues in the two PLS clusters. 
    more » « less
  5. ; ; ; (, Chemical Science)
    Observation of super-Nernstian proton-coupled electron transfer behavior with two protons per electron transferred in an electrochemically n-doped redox conjugated polymer. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Text Encoded Conversion
  • XML
  • Save / Share this Record
  • Send to Email