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Search Publications by: Craig Brown (Fed)

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Displaying 101 - 125 of 309

Anharmonic Acoustic Phonons and A-site Critical Fluctuations in the Lead Halide Perovskite CsPbBr 3

September 17, 2019
Author(s)
M. Songvilay, Nathan Giles-Donovan, M. Bari, Z.-G. Ye, J. L. Minns, M. A. Green, Guangyong Xu, Peter M. Gehring, K. Schmalzl, William D. Ratcliff, Craig Brown, D. Chernyshov, W. van Beek, Sandy Cochran, Christopher Stock
We apply neutron spectroscopy to investigate the transverse acoustic phonons in the lead halide CsPbBr 3 near the three zone boundaries of the cubic Pm3m Brillouin zone at QX = (2,1/2,0), Q M = (3/2,1/2,0), and Q R = (1/2,1/2,3/2). CsPbB r3 undergoes two

Accessing New Charge-Transfer Complexes by Mechanochemistry: A Tetrathiafulvalene Chloranilic Acid Polymorph Containing Segregated Tetrathiafulvalene Stacks

September 4, 2019
Author(s)
Jeffrey Jones, Vinh Ta Phuoc, Leire del Campo, Nestor E. Massa, Craig Brown, Silvina Pagola
Two polymorphs of tetrathiafulvalene chloranilic acid (ITF-CAH 2) have been synthesized by mechanochemistry. The previously known "ionic" polymorph (form I), was prepared by liquid assisted grinding (LAG) using various highly polar solvents; as well as

Understanding Gas Storage in Cuboctahedral Porous Coordination Cages

July 4, 2019
Author(s)
Gregory R. Lorzing, Eric J. Gosselin, Benjamin Trump, Arthur H. P. York, Arni Sturluson, Casey A. Rowland, Glenn P. A. Yap, Craig Brown, Cory M. Simon, Eric D. Bloch
Porous molecular solids are promising molecular solids are promising materials for gas storage applications. However, given the relative dearth of studies concerning these materials in this regard, additional adsorption and structural studies are vital for

Competing Polar and Antipolar Structures in the Ruddlesden-Popper Layered Perovskite Li 2 SrNb 2 O 7

June 25, 2019
Author(s)
Ritesh Uppuluri, Hirofumi Akamatsu, Arnab Sen Gupta, Huaiyu Wang, Craig Brown, Kleyser E. Agueda Lopez, Nasim Alem, Venkatraman Gopalan, Thomas E. Mallouk
Over the past few years, several studies have reported the existence of polar phase in n=2 Ruddlesden-Popper layer perovskites by trilinear coupling of oxygen octahedral rotations (OOR) and polar distortions, a phenomenon termed as hybrid improper

High-Pressure Synthesis of Non-Stoichiometric Li x WO 3 (0.5less than or equal to}xless than or equal to}1.0) with LiNbO 3 Structure

May 12, 2019
Author(s)
Kohdai Ishida, Yuya Ikeuchi, Cedric Tassel, Hiroshi Takatsu, Craig Brown, Hiroshi Kageyama
Compounds with the LiNbO 3-type structure are important for a variety of applications such as piezoelectric sensors, while recent attention has been paid to magnetic and electronic properties. However, all the materials reported are stoichiometric. This

Rattling Behavior in a Simple Perovskite NaWO 3

May 1, 2019
Author(s)
Yuya Ikeuchi, Hiroshi Takatsu, Cedric Tassel, Craig Brown, Taito Murakami, Yuki Matsumoto, Yoshihiko Okamoto, Hiroshi Kageyama
A high-pressure reaction has allowed the preparation of stoichiometric tungsten bronze NaWO 3 (Im-3). Specific heat (C ;/T 3 vs T) exhibits a round peak at 30 K, indicating anharmonic phonon modes associated with low-energy rattling vibrations. Structural

New Insights into Water Dynamics of Portland Cement Paste with Nano-Additives using Quasielastic Neutron Scattering

March 1, 2019
Author(s)
Kunal Kupwade-Patil, Ali Bumajdad, Craig Brown, Madhu Sudan Tyagi, Nicholas Butch, Abdullah F. Jamsheer, Oral Buyukozturk
Early age hydration kinetics of Portland cement with nano additives such as nano-silica (NS) was examined using quasielastic neutron scattering (QENS). Cement pastes with different ratios of Portland cement to NS was prepared. The concentration of the NS

Neutron Instruments for Research in Coordination Chemistry

February 28, 2019
Author(s)
Zi-Ling Xue, Anibal J. Ramirez-Cuesta, Craig Brown, Stuart Calder, Huibo Cao, Bryan C. Chakoumakos, Luke L. Daemen, Ashfia Huq, Alexander I. Kolesnikov, Eugene Mamontov, Andrey A Podlesnyak, Xiaoping Wang
Neutron diffraction and spectroscopies offer unique insight into structures and properties of solids and molecular materials. All neutron instruments located at the various neutron sources are distinct, even if their designs are based on similar principles

Probing Magnetic Excitations in Co^II^ Single-Molecule Magnets by Inelastic Neutron Scattering

February 27, 2019
Author(s)
Shelby E. Stavretis, Yongqiang Cheng, Luke L. Daemen, Craig Brown, Duncan H. Moseley, Eckhard Bill, Mihail Atanasov, A. J. Ramirez-Cuesta, Frank Neese, Zi-Ling Xue
Co(acac) 2(H 2O) 2 (1 acac = acetylacetonate), a transition metal complex (S = 3/2), displays field-induced slow magnetic relaxation as a single-molecule magnet (SMMs). For 1 and its isotopologues Co(acac) 2(D 2O) 2 (1-d 4^) and Co(acac-d 7) 2(D 2O) 2 (1-D

Ni 2 Mo 3 O 8 : Complex Antiferromagnetic Order on a Honeycomb Lattice

January 18, 2019
Author(s)
Jennifer R. Morey, Allen Scheie, John P. Sheckelton, Craig Brown, Tyrel M. McQueen
Theoretical studies have predicted the existence of topological magnons in honeycomb compounds with zig-zag antiferromagnetic (AFM) order. Here we report this discovery of zig-zag AFM order in the layered and non-centrosymmetric honeycomb nickelate Ni 2Mo

High-Pressure Synthesis of A 2 NiO 2 Ag 2 Se 2 (A=Sr, Ba) with a High-Spin Ni 2+ in Square-Planar Coordination

January 14, 2019
Author(s)
Yuki Matsumoto, Takafumi Yamamoto, Kousuke Nakano, Hiroshi Takatsu, Taito Murakami, Kenta Hongo, Ryo Maezono, Hiraku Ogino, Dongjoon Song, Craig Brown, Tassel Cedric, Hiroshi Kageyama
Square-planar coordinate Ni 2+ ions in oxides are exclusively limited to a low spin state (S = 0) owing to extensive crystal field splitting. Here we report layered oxychalcogenides A 2NiO 2Ag 2Se 2 (A = Sr, Ba) with the S = 1 NiO 2 square lattice. The