Results for “BaMnSb2” | Engineering Papers

DOE OSTI2020

Materials Data on BaMnSb2 by Materials Project

BaMnSb2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are three inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight Sb2- atoms. All Ba–Sb bond lengths are 3.62 Å. In the second Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight Sb2- atoms. All Ba–Sb bond lengths are 3.62 Å. In the third Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight Sb2- atoms. All Ba–Sb bond lengths are 3.62 Å. Mn2+ is bonded to four Sb2- atoms to form a mixture of corner and edge-sharing MnSb4 tetrahedra. All Mn–Sb bond lengths are 2.75 Å. There are eight inequivalent Sb2- sites. In the first Sb2- site, Sb2- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Mn2+ atoms. In the second Sb2- site, Sb2- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Mn2+ atoms. In the third Sb2- site, Sb2- is bonded in a distorted body-centered cubic geometry to four Ba2+ and four equivalent Sb2- atoms. All Sb–Sb bond lengths are 3.17 Å. In the fourth Sb2- site, Sb2- is bonded in a distorted body-centered cubic geometry to four Ba2+ and four equivalent Sb2- atoms. In the fifth Sb2- site, Sb2- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Mn2+ atoms. All Sb–Ba bond lengths are 3.62 Å. All Sb–Mn bond lengths are 2.75 Å. In the sixth Sb2- site, Sb2- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Mn2+ atoms. All Sb–Mn bond lengths are 2.75 Å. In the seventh Sb2- site, Sb2- is bonded in a distorted body-centered cubic geometry to four equivalent Ba2+ and four equivalent Sb2- atoms. All Sb–Sb bond lengths are 3.17 Å. In the eighth Sb2- site, Sb2- is bonded in a distorted body-centered cubic geometry to four equivalent Ba2+ and four equivalent Sb2- atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Phonon Helicity Induced by Electronic Berry Curvature in Dirac Materials

In two-dimensional insulators with time-reversal (TR) symmetry, a nonzero local Berry curvature of low-energy massive Dirac fermions can give rise to nontrivial spin and charge responses, even though the integral of the Berry curvature over all occupied states is zero. In this Letter, we present a new effect induced by the electronic Berry curvature. By studying electron-phonon interactions in BaMnSb2, a prototype two-dimensional Dirac material possessing two TR-related massive Dirac cones, we find that the nonzero local Berry curvature of electrons can induce a phonon angular momentum. The direction of this phonon angular momentum is locked to the phonon propagation direction, and thus we refer to it as “phonon helicity” in a way that is reminiscent of electron helicity in spin-orbit-coupled electronic systems. We discuss possible experimental probes of such phonon helicity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2021

Building Neutron Scattering Infrastructure in Louisiana for Advanced Materials (Final Report)

The main objective of the Louisiana Consortium for Neutron Scattering (LaCNS) is to build a major neutron scattering infrastructure capable of treating both soft and hard materials. The goal is to create a sustainable effort having the quality, breadth, and depth necessary to produce competitive proposals including collaborative and center type proposals. Our scientific aim is to understand the role of coupling in emergent complex materials and its impact on the structure/property relationship and to explore how to tune the key couplings to guide the design of materials with the desired properties. This naturally includes building a base of users of the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR) in Louisiana; to train highly talented graduate and post-doctoral students in synthesis, neutron scattering, and simulation and modeling techniques, thereby helping to produce the next generation of scientist who use neutron scattering techniques as a crucial part of their research. The goal of our hard matter program is to understand the interplay between spin, charge, orbital, and lattice degrees of freedom in carefully selected complex materials. We have made considerable progress on number of complex systems including the oxide Sr3(Ru1-xMnx)2O7 where short-range magnetic ordering with anisotropic spin texture is initiated at the metal-insulator transition that clearly indicates a strong spin-charge coupling. Another critical area is in quantum materials. For example, in the topological semimetal BaMnSb2, we found a 3D canted antiferromagnetic Weyl semimetal with a 2D electronic structure and a nontrivial Berry phase. In addition, in the hexagonal chiral Mn1/3NbS2 system, we found soliton/soliton and soliton/antisoliton domain walls where the application of small fields or small currents can be used to control nanoscopic magnetic domains where the control of domain walls is crucially important for information storage. In addition, chemical transformation investigations were performed on the VISION instrument at Spallation Neutron Source (SNS). The soft matter effort was focused on understanding the role of non-covalent interactions on the structure and dynamics of fluid-based soft matter. One key focus was on sequence-defined (SD) amphiphilic peptoid polymers that allow encoding of molecular interactions and thereby systematic investigations of how charge directs the solution self-assembly of amphiphilic polymers in water. Another important area was on the dynamics of lipids self-assembled into membranes for exploring the permeability and mechanical using both neutron spin echo (NSE) spectroscopy and quasielastic neutron scattering (QENS) to distinguished between viscoelasticity and permeability at the molecular scale. Overall, the LaCNS project was quite successful, generating 145 publications and 245 presentations. Our graduate and post-doctoral students were well trained resulting in positions in national laboratories (Oak Ridge National Laboratory (ORNL), Argonne National Laboratory and Los Alamos National Laboratory), major research universities, and industry. We also developed a uniaxial pressure cell along with ORNL for SNS. A critical goal of this project was to establish a foundation for competing nationally in federally funded research programs. To this end, we were quite successful in generating over twenty-two federally and non-federally funded grants including awards from NSF, DOE, and DOD, and two early career awards. Equally important, we were able to secure a key major piece of instrumentation via a large ARO grant for a state-of-the-art electron microscope.

36 MATERIALS SCIENCE↗