scholarly journals Structural Distortion Stabilizing the Antiferromagnetic and Insulating Ground State of NiO

Symmetry ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 56 ◽  
Author(s):  
Ekkehard Krüger
Keyword(s):  
Fermi Level ◽  
Ground State ◽  
Small Deformation ◽  
Structural Distortion ◽  
Inversion Symmetry ◽  
Time Inversion ◽  
Antiferromagnetic Phase ◽  
Antiferromagnetic State ◽  
Space Group ◽  
Perfect Symmetry

We report evidence that the experimentally observed small deformation of antiferromagnetic NiO modifies the symmetry of the crystal in such a way that the antiferromagnetic state becomes an eigenstate of the electronic Hamiltonian. This deformation closely resembles a rhombohedral contraction, but does not possess the perfect symmetry of a trigonal (rhombohedral) space group. We determine the monoclinic base centered magnetic space group of the antiferromagnetic structure within the deformed crystal which is strongly influenced by the time-inversion symmetry of the Hamiltonian. The antiferromagnetic state is evidently stabilized by a nonadiabatic atomic-like motion of the electrons near the Fermi level. This atomic-like motion is characterized by the symmetry of the Bloch functions near the Fermi level and provides in NiO a perfect basis for a Mott insulator in the antiferromagnetic phase.

scholarly journals Wannier States of FCC Symmetry Qualifying Paramagnetic NiO to Be a Mott Insulator

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 687 ◽  
Author(s):  
Ekkehard Krüger
Keyword(s):  
Ground State ◽  
Energy Band ◽  
Mott Insulator ◽  
Paramagnetic Phase ◽  
Localized States ◽  
Structural Distortion ◽  
Antiferromagnetic Phase ◽  
Antiferromagnetic State ◽  
Compound I ◽  
Wannier Functions

This letter extends my recent paper on antiferromagnetic NiO [Structural Distortion Stabilizing the Antiferromagnetic and Insulating Ground State of NiO, Symmetry 2020, 12(1), 56] by including also the paramagnetic phase of this compound. I report evidence that paramagnetic NiO possesses a narrow, roughly half-filled energy band that produces a nonadiabatic atomic-like motion providing the basis for a Mott insulator in the paramagnetic phase. While the atomic-like motion operating in the antiferromagnetic phase is adapted to the symmetry of the antiferromagnetic state, in the paramagnetic phase, the related localized states are represented by optimally localized Wannier functions possessing the full fcc symmetry of paramagnetic NiO. The nonadiabatic Wannier states are twofold degenerate, have d-like symmetry, and are situated at the Ni atoms.

Magnetic Ground State and Electronic Structure Calculations of PbMnO3 Using DFT

2014 ◽  
Vol 895 ◽  
pp. 420-423 ◽  
Author(s):  
Sathya Sheela Subramanian ◽  
Baskaran Natesan
Keyword(s):  
Electronic Structure ◽  
Band Structure ◽  
Fermi Level ◽  
Ground State ◽  
Density Functional ◽  
Electronic Structure Calculations ◽  
Magnetic Ground State ◽  
Electronic Band ◽  
Structure Calculations ◽  
Centrosymmetric Structure

Structural optimization, magnetic ground state and electronic structure calculations of tetragonal PbMnO3have been carried out using local density approximation (LDA) implementations of density functional theory (DFT). Structural optimizations were done on tetragonal P4mm (non-centrosymmetric) and P4/mmm (centrosymmetric) structures using experimental lattice parameters and our results indicate that P4mm is more stable than P4/mmm. In order to determine the stable magnetic ground state of PbMnO3, total energies for different magnetic configurations such as nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) were computed for both P4mm and P4/mmm structures. The total energy results reveal that the FM non-centrosymmetric structure is found to be the most stable magnetic ground state. The electronic band structure, density of states (DOS) and the electron localization function (ELF) were calculated for the stable FM structure. ELF revealed the distorted non-centrosymmetric structure. The band structure and DOS for the majority spins of FM PbMnO3showed no band gap at the Fermi level. However, a gap opens up at the Fermi level in minority spin channel suggesting that it could be a half-metal and a potential spintronic candidate.

scholarly journals Crystal structures of (2E)-1-(3-bromothiophen-2-yl)-3-(2-methoxyphenyl)prop-2-en-1-one and (2E)-1-(3-bromothiophen-2-yl)-3-(3,4-dimethoxyphenyl)prop-2-en-1-one

2015 ◽  
Vol 71 (8) ◽  
pp. 965-971 ◽  
Author(s):  
Vasant S. Naik ◽  
Venkataraya Shettigar ◽  
Tyler S. Berglin ◽  
Jillian S. Coburn ◽  
Jerry P. Jasinski ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Intermolecular Interactions ◽  
Intramolecular Interaction ◽  
Intramolecular Interactions ◽  
Inversion Symmetry ◽  
Stacking Interactions ◽  
Asymmetric Unit ◽  
Space Group ◽  
Independent Molecules

In the molecules of the title compounds, (2E)-1-(3-bromo-thiophen-2-yl)-3-(2-methoxyphenyl)prop-2-en-1-one, C14H11BrO2S, (I), which crystallizes in the space groupP-1 with four independent molecules in the asymmetric unit (Z′ = 8), and (2E)-1-(3-bromothiophen-2-yl)-3-(3,4-dimethoxyphenyl)prop-2-en-1-one, C15H13BrO3S, (II), which crystallizes withZ′ = 8 in the space groupI2/a, the non-H atoms are nearly coplanar. The molecules of (I) pack with inversion symmetry stacked diagonally along thea-axis direction. Weak C—H...Br intramolecular interactions in each of the four molecules in the asymmetric unit are observed. In (II), weak C—H...O, bifurcated three-center intermolecular interactions forming dimers along with weak C—H...π and π–π stacking interactions are observed, linking the molecules into sheets along [001]. A weak C—H...Br intramolecular interaction is also present. There are no classical hydrogen bonds present in either structure.

Structural Systematics of Metal Acetylide Complexes: X-Ray Studies of Some 'Extended-Chain' Gold σ-Acetylide Complexes

1997 ◽  
Vol 50 (10) ◽  
pp. 991 ◽  
Author(s):  
Ian R. Whittall ◽  
Mark G. Humphrey ◽  
David C. R. Hockless
Keyword(s):  
Ground State ◽  
Structural Data ◽  
Monoclinic Space Group ◽  
Confidence Limits ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
Space Group ◽  
X Ray ◽  
Back Bonding ◽  
Ground State Geometry

The structures of Au(4-C≡CC6H4XYC6H4-4′-NO2)(PPh3) (XY = (E )-CH=CH (1), (Z)-CH=CH (2), C≡C (3), N=CH (4)) have been determined by single-crystal X-ray diffraction analyses, refining by full-matrix least-squares analysis. For (1), crystals are triclinic, space group P-1, with a8·847(1), b 17·870(4), c 19·705(3) Å, α116·25(1), β 93·33(1), γ 92·64(2)˚, Z 4, 6747 unique reflections (703 parameters), converging at R 0·025 and Rw 0·029. For (2), crystals are monoclinic, space group P 21/a, with a 10·718(6), b 19·398(5), c14·469(3) Å, β 108·96(2)˚, Z 4, 3295 unique reflections (352 parameters), converging atR 0·040 and Rw 0·034. For (3), crystals are triclinic, space group P-1, with a 10·671(4), b 17·599(7), c 18·220(8) Å, α 116·31(3), β 105·00(4), γ 95·08(4)˚, Z 4, 4828 unique reflections (703 parameters), converging at R 0·043 and Rw 0·030. For (4), crystals are triclinic, space group P-1, with a 8·8314(6), b 17·834(2), c 20·001(2) Å, α 115·249(7), β 90·930(7), γ 94·082(7)˚, Z 4, 4724 unique reflections (703 parameters), converging at R 0·035 and Rw 0·034. Despite the [ligated metal donor]-bridge-[nitro acceptor] composition of these complexes, Au–C and C≡C distances are normal and consistent with minimal allenylidene contribution to the ground-state geometry. Within the 3σ confidence limits, the structural data do not provide evidence for π*-back-bonding in these complexes

Die Struktur von Bis(cyclopentadienyldicarhonylmangan)-1.2-diphenyldiphosphan, [C5H5(CO)2Mn]2PhP(H)—(H)PPh.

1976 ◽  
Vol 31 (9) ◽  
pp. 1166-1169 ◽  
Author(s):  
G. Huttner ◽  
H.-D. Müller ◽  
Vera Bejenke ◽  
O. Orama
Keyword(s):  
Title Compound ◽  
Inversion Symmetry ◽  
Full Matrix ◽  
Space Group

The title compound 1 contains complex stabilized 1,2-diphenyldiphosphane. It crystallizes in space group P21/c with a = 1095(1), b = 1145(1), c = 1186(1) pm, β= 124.73(5)°, Z = 2. The structure has been solved by coventional methods; full matrix refinement converged at R1= 0.045.1 shows crystallographic inversion symmetry and thus contains a meso-1,2-diphenyldiphosphane ligand. The P–P-distance is 225.8 pm, the Mn–P bonds are rather short (221.6 pm).

Synthesis and crystal chemistry of the new compounds GdBa4Cu3O8.5+δ and DyBa4Cu3O8.5+δ

1999 ◽  
Vol 14 (2) ◽  
pp. 334-339 ◽  
Author(s):  
Y. T. Zhu ◽  
E. J. Peterson ◽  
P. S. Baldonado ◽  
J. Y. Coulter ◽  
D. E. Peterson ◽  
...  
Keyword(s):  
Quantum Interference ◽  
Lattice Parameter ◽  
Inversion Symmetry ◽  
Iodometric Titration ◽  
Powder Diffraction Data ◽  
Superconducting Quantum Interference Device ◽  
Space Group ◽  
X Ray ◽  
Space Groups ◽  
New Compounds

Two new compounds, GdBa4Cu3O8.5+δ (Gd143) and DyBa4Cu3O8.5+δ (Dy143), were synthesized from precursors Gd2O3, Dy2O3, BaO2, and CuO at 1000 °C in an oxygen atmosphere. The oxygen stoichiometric value δ was found to be 0.68 for Gd143 and 0.6 for Dy143 by iodometric titration. Rietveld refinement of x-ray powder diffraction data showed that Gd143 belongs to the space group Pm3 while Dy143 belongs to the space group P23. The two space groups, Pm3 and P23, are very similar. Their main difference is that P23 does not have the inversion symmetry of Pm3. Both compounds have a cubic unit cell with a lattice parameter of 8.16528 ± 0.00006 Å for Gd143 and 8.10807 ± 0.00010 Å for Dy143. Superconducting quantum interference device (SQUID) measurement indicated that neither compound was superconductive down to 5 K.

EFFECTS OF IN-PLANE STRAIN ON MAGNETISM IN LaMnO3 THIN FILMS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3281-3284 ◽  
Author(s):  
K. H. AHN ◽  
A. J. MILLIS
Keyword(s):  
Thin Films ◽  
Magnetic Properties ◽  
Plane Strain ◽  
Elastic Energy ◽  
Ground State ◽  
Lattice Mismatch ◽  
Tight Binding ◽  
Antiferromagnetic State ◽  
Magnetic Ground State ◽  
Lattice Coupling

The effects of the in-plane strain on the magnetic properties of LaMnO3 thin films are calculated using an elastic energy expression and a tight binding Hamiltonian with electron-lattice coupling. Tensile uniaxial strain of the order of 2%, which is the order of the magnitude of those induced in thin films by lattice mismatch with substrates, is found to change the magnetic ground state from A-type antiferromagnetic state to purely antiferromagnetic state.

scholarly journals Superconductivity coexisting with ferromagnetism in a quasi-one dimensional non-centrosymmetric (TaSe4)3I

2021 ◽  
Author(s):  
Atindra Pal ◽  
Arnab Bera ◽  
Sirshendu Gayen ◽  
Suchanda Mondal ◽  
Riju Pal ◽  
...  
Keyword(s):  
Direct Consequence ◽  
Meissner Effect ◽  
Inversion Symmetry ◽  
Quantum Phases ◽  
Space Group ◽  
Triplet Pairing ◽  
Spin Triplet ◽  
Low Dimensional ◽  
Magnetic Insulator ◽  
First Time

Abstract Low-dimensional materials with broken inversion symmetry and strong spin-orbit coupling can give rise to fascinating quantum phases and phase transitions. Here we report coexistence of superconductivity and ferromagnetism below 2.5 K in the quasione dimensional crystals of non-centrosymmetric (TaSe4)3I (space group: P¯421c). The unique phase is a direct consequence of inversion symmetry breaking as the same material also stabilizes in a centro-symmetric structure (space group: P4/mnc) where it behaves like a non-magnetic insulator[1–4]. The coexistence here upfront contradicts the popular belief that superconductivity and ferromagnetism are two apparently antagonistic phenomena. Notably, here, for the first time, we have clearly detected Meissner effect in the superconducting state despite the coexisting ferromagnetic order. The coexistence of superconductivity and ferromagnetism projects non-centrosymmetric (TaSe4)3I as a host for complex ground states of quantum matter including possible unconventional superconductivity with elusive spin-triplet pairing[5–8].

Sign in / Sign up

Export Citation Format

Share Document