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Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations
Magnetic skyrmions, which are topologically distinct magnetic spin textures, are gaining increased attention for their unique physical properties and potential applications in spintronic devices. Here we present a design strategy for skyrmion host candidates based on combinations of magnetic spin, asymmetric building units having stereoactive lone-pair electrons, and polar lattice symmetry. To demonstrate the viability of the proposed rational design principles, we successfully synthesized a Fe(IO 3 ) 3 polycrystalline sample and single crystals by using a new simplified low-temperature pathway, which is experimentally feasible for extending materials growth of transition metal iodates. Single crystal X-ray and powder synchrotron X-ray diffraction measurements demonstrated that Fe(IO 3 ) 3 crystallizes in the polar chiral hexagonal lattice with space group P63. The combined structural features of the macroscopic electric polarization along the c-axis stemming from the coalignment of the stereoactive lone-pairs of the IO 3 – trigonal pyramid and the magnetic Fe 3+ cation residing on the 3-fold rotation axis were selected to promote asymmetric exchange coupling. We find evidence of a predicted skyrmion phase at 14 K ≤ T ≤ 16 K and 2.5 T ≤ μ 0 H ≤ 3.2 T driven by a Dzyaloshinskii–Moriya (DM) interaction, a conclusion supported by the appreciable DM exchange and the zero-field spiral antiferromagnetic ground state of Fe(IO 3 ) 3 deduced from neutron diffraction experiments. The associated magnetic modulation wavelength of the putative skyrmions is expected to be short ~18 nm, comparable to the period of the DM-driven incommensurate order. This work links stereoactive lone-pair electron effects to enhanced DM interaction, demonstrating a new approach for chemical guidelines in the search for skyrmionic states of matter.
Fe3Sb5(O3I)3 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one Fe3Sb5(O3I)3 sheet oriented in the (0, 1, 0) direction. there are three inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded in a 5-coordinate geometry to three O2- and two I1- atoms. There are a spread of Fe–O bond distances ranging from 1.97–2.16 Å. There are one shorter (2.87 Å) and one longer (3.06 Å) Fe–I bond lengths. In the second Fe3+ site, Fe3+ is bonded in a distorted see-saw-like geometry to four O2- and one I1- atom. There are a spread of Fe–O bond distances ranging from 2.05–2.20 Å. The Fe–I bond length is 3.15 Å. In the third Fe3+ site, Fe3+ is bonded in a 5-coordinate geometry to five O2- and one I1- atom. There are a spread of Fe–O bond distances ranging from 2.04–2.34 Å. The Fe–I bond length is 3.00 Å. There are five inequivalent Sb+2.40+ sites. In the first Sb+2.40+ site, Sb+2.40+ is bonded in a 3-coordinate geometry to three O2- and one I1- atom. There are a spread of Sb–O bond distances ranging from 1.99–2.13 Å. The Sb–I bond length is 3.16 Å. In the second Sb+2.40+ site, Sb+2.40+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Sb–O bond distances ranging from 2.07–2.61 Å. In the third Sb+2.40+ site, Sb+2.40+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Sb–O bond distances ranging from 2.01–2.10 Å. In the fourth Sb+2.40+ site, Sb+2.40+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Sb–O bond distances ranging from 2.03–2.23 Å. In the fifth Sb+2.40+ site, Sb+2.40+ is bonded in a 3-coordinate geometry to three O2- atoms. There are one shorter (2.01 Å) and two longer (2.04 Å) Sb–O bond lengths. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Fe3+ and two Sb+2.40+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to three Sb+2.40+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three Sb+2.40+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Fe3+ and two Sb+2.40+ atoms. In the fifth O2- site, O2- is bonded to three Fe3+ and one Sb+2.40+ atom to form a mixture of edge and corner-sharing OFe3Sb tetrahedra. In the sixth O2- site, O2- is bonded in a trigonal non-coplanar geometry to one Fe3+ and two equivalent Sb+2.40+ atoms. In the seventh O2- site, O2- is bonded to three Fe3+ and one Sb+2.40+ atom to form a mixture of edge and corner-sharing OFe3Sb tetrahedra. In the eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Fe3+ and two Sb+2.40+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Fe3+ and two Sb+2.40+ atoms. There are three inequivalent I1- sites. In the first I1- site, I1- is bonded in a 1-coordinate geometry to two Fe3+ atoms. In the second I1- site, I1- is bonded in a distorted single-bond geometry to one Fe3+ atom. In the third I1- site, I1- is bonded in a 1-coordinate geometry to one Fe3+ and one Sb+2.40+ atom.
Several different types of aerogel and/or xerogel scaffolds have been demonstrated as effective sorbents for the capture and immobilization of radionuclides in gaseous form [e.g., iodine gas or I2(g), Xe] as well as ionic form (e.g., Ce4+, Cs+, I–, IO3-, Rb+, Sr2+, 99Tc7+, and U6+). These scaffolds have unique properties, which include high specific surface areas, high pore volumes, varieties of pore sizes, and functionalities that provide methods for binding radionuclides through physisorption, chemisorption, or a combination thereof. This combination of properties and functionalities make these types of materials ideal scaffolds for use as sorbents for capturing radionuclides. The primary base materials that will be discussed in this chapter include Ag0-functionalized silica aerogels, Ag+-impregnated aluminosilicate aerogels, Ag0-functionalized aluminosilicate aerogels, metal-impregnated (non-Ag) aluminosilicate aerogels and xerogels, sulfide-based aerogels, and carbon-based aerogel composites. For the capture of I2(g), the materials reported herein show some of the highest iodine loadings ever reported for inorganic sorbents. For the capture of ionic species, these materials also show promise to be some of the next generations of materials for active radionuclide remediation. This progress report will describe how these materials are fabricated, the general properties of these materials, as well as an overview of how they have been used for different applications in environmental remediation of radionuclides.