1
|
Müller PC, Elliott SR, Dronskowski R, Jones RO. Chemical bonding in phase-change chalcogenides. J Phys Condens Matter 2024; 36:325706. [PMID: 38697198 DOI: 10.1088/1361-648x/ad46d6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2024] [Accepted: 05/02/2024] [Indexed: 05/04/2024]
Abstract
Almost all phase-change memory materials (PCM) contain chalcogen atoms, and their chemical bonds have been denoted both as 'electron-deficient' [sometimes referred to as 'metavalent'] and 'electron-rich' ['hypervalent', multicentre]. The latter involve lone-pair electrons. We have performed calculations that can discriminate unambiguously between these two classes of bond and have shown that PCM have electron-rich, 3c-4e ('hypervalent') bonds. Plots of charge transferred between (ET) and shared with (ES) neighbouring atoms cannot on their own distinguish between 'metavalent' and 'hypervalent' bonds, both of which involve single-electron bonds. PCM do not exhibit 'metavalent' bonding and are not electron-deficient; the bonding is electron-rich of the 'hypervalent' or multicentre type.
Collapse
Affiliation(s)
- P C Müller
- Lehrstuhl für Festkörper- and Quantenchemie, Institut für Anorganische Chemie, RWTH Aachen University, D-52056 Aachen, Germany
| | - S R Elliott
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford OX1 3QZ, United Kingdom
| | - R Dronskowski
- Lehrstuhl für Festkörper- and Quantenchemie, Institut für Anorganische Chemie, RWTH Aachen University, D-52056 Aachen, Germany
| | - R O Jones
- Peter-Grünberg-Institut PGI-1, Forschungszentrum Jülich, D-52425 Jülich, Germany
| |
Collapse
|
2
|
Cheranovskii VO, Slavin VV, Tchougréeff AL, Dronskowski R. The gapless energy spectrum and spin-Peierls instability of 1D Heisenberg spin systems in polymeric complexes of transition metals and hypothetical carbon allotropes. J Phys Condens Matter 2019; 31:305601. [PMID: 30986772 DOI: 10.1088/1361-648x/ab197a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We investigate the spin-Peierls instability of some periodic 1D Heisenberg spin systems having a gapless energy spectrum at different values of coupling J between the unit cells. Using the density-matrix renormalization group method we numerically study the dependence of critical exponents p of spin-Peierls transition of above spin systems on the value of J. In contrast to chain systems, we find significantly non-monotonous dependence p (J) for three-legs ladder system. In the limit of weak coupling J we derive effective spin s chain Hamiltonians describing the low-energy states of the system considered by means of perturbation theory. The value of site spin s coincides with the value of the ground-state spin of the isolated unit cell of the system considered. This means that at small J values all the systems with the singlet ground state and the same half-integer value of s should have a similar critical behavior which is in agreement with our numerical study. The presence of gapped excitations inside the unit cells at small values of J should give, for our spin systems, at least one intermediate plateau in field dependence of magnetization at low temperatures. The stability of this plateau against the increase of the values of J and temperature is studied using the quantum Monte-Carlo method.
Collapse
Affiliation(s)
- V O Cheranovskii
- V N Karazin Kharkiv National University, 61022 Svoboda Sq.4, Kharkiv, Ukraine
| | | | | | | |
Collapse
|
3
|
Benz S, Möller A, Marioneck T, Hofmann M, Brenk J, Dronskowski R. Construction of a hybrid clamped cell for high-pressure neutron-diffraction experiments with a large diamond window. Rev Sci Instrum 2019; 90:026103. [PMID: 30831751 DOI: 10.1063/1.5066365] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 01/24/2019] [Indexed: 06/09/2023]
Abstract
A hybrid pressure cell was fabricated from commercially available copper-beryllium and custom-made Ni-Cr-Al Russian alloy, tailored for usage as a reaction vessel supplying a volume of about 400 mm3. In order to directly (in situ) monitor pressure and chemical reactions within the chamber, a large diamond window suitable for spectroscopic sample analysis was implemented. The performance of the hybrid cell was validated from high-pressure neutron-diffraction measurements on carbon dioxide.
Collapse
Affiliation(s)
- S Benz
- Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen, Germany
| | - A Möller
- Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen, Germany
| | - T Marioneck
- Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen, Germany
| | - M Hofmann
- Research Neutron Source Heinz Maier-Leibnitz (FRM II), Technical University Munich, D-85748 Garching, Germany
| | - J Brenk
- Institute IME Process Metallurgy and Metal Recycling, RWTH Aachen University, 52056 Aachen, Germany
| | - R Dronskowski
- Chair of Solid-State and Quantum Chemistry, Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen, Germany
| |
Collapse
|
4
|
Mroz D, George J, Kremer M, Wang R, Englert U, Dronskowski R. A new tool for validating theoretically derived anisotropic displacement parameters with experiment: directionality of prolate displacement ellipsoids. CrystEngComm 2019. [DOI: 10.1039/c9ce00794f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
How well do anisotropic displacement parameters from theory match experiment? The orientation of prolate ellipsoids contributes to the answer!
Collapse
Affiliation(s)
- D. Mroz
- Institute of Inorganic Chemistry
- D-52056 Aachen
- Germany
| | - J. George
- Institute of Condensed Matter and Nanoscience
- Université Catholique de Louvain
- 1348 Louvain-la-Neuve
- Belgium
| | - M. Kremer
- Institute of Inorganic Chemistry
- D-52056 Aachen
- Germany
| | - R. Wang
- Institute of Inorganic Chemistry
- D-52056 Aachen
- Germany
- Institute of Molecular Science
- Shanxi University
| | - U. Englert
- Institute of Inorganic Chemistry
- D-52056 Aachen
- Germany
- Institute of Molecular Science
- Shanxi University
| | - R. Dronskowski
- Institute of Inorganic Chemistry
- D-52056 Aachen
- Germany
- Jülich-Aachen Research Alliance (JARA-HPC)
- RWTH Aachen University
| |
Collapse
|
5
|
Herrmann MG, Stoffel RP, Dronskowski R, Friese K. The low-temperature heat capacity of the Sb 2Te 3-x Se x solid solution from experiment and theory. J Phys Condens Matter 2018; 30:405702. [PMID: 30168444 DOI: 10.1088/1361-648x/aade0e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The lattice dynamics of Sb2Te3-x Se x (x = 0, 0.6, 1.2, 1.8, 3) mixed crystals have been studied by a combination of low-temperature heat-capacity measurements between 2-300 K and first-principles calculations. The results from the experimental and theoretical investigations are in excellent agreement. While Sb2Se3 can be considered as a harmonic lattice oscillator in this temperature range, for the isostructural compounds Sb2Te3, Sb2Se0.6Te2.4, Sb2Se1.2Te1.8 and Sb2Se1.8Te1.2 (tetradymite structure type; R [Formula: see text] m) a small anharmonic contribution to the total heat capacity has to be taken into account at temperatures above 250 K. For the compounds which crystallize in the tetradymite structure type the experimental and theoretical data show unambiguously that the exchange of Te by Se leads to an increase of the bonding polarity and consequently to a hardening of the bonding which is reflected in an increase of the Debye temperatures with increasing Se contents. In addition, our studies clearly demonstrate that the mixed crystals in the stability field of the tetradymite structure type are characterized by a strong non-ideal mixing behavior.
Collapse
Affiliation(s)
- M G Herrmann
- Jülich Centre for Neutron Science-2/Peter Grünberg Institut-4, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | | | | | | |
Collapse
|
6
|
Abstract
Cooling within gloveboxes is often restricted to expensive refrigerated bath circulators or small temperature differences. Here, we present a sturdy, inexpensive cooling system which matches various glovebox types and can be readily fabricated by a mechanical workshop in a few days. The system is suitable for cold plates of areas up to 150 cm2 and temperatures as low as -100 °C.
Collapse
Affiliation(s)
- A Möller
- Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen, Germany
| | - T Marioneck
- Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen, Germany
| | - R Dronskowski
- Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen, Germany
| |
Collapse
|
7
|
Affiliation(s)
- A. L. Tchougréeff
- Chair of Solid-State and Quantum Chemistry, Institut für anorganische Chemie, RWTH-Aachen University, Aachen, Germany
- Moscow Center for Continuous Mathematical Education, Moscow, Russia
- Department of Chemistry, Moscow State University, Moscow, Russia
| | - R. Dronskowski
- Chair of Solid-State and Quantum Chemistry, Institut für anorganische Chemie, RWTH-Aachen University, Aachen, Germany
| |
Collapse
|
8
|
Schilling H, Wolff H, Dronskowski R, Lerch M. Fluorite-Type Solid Solutions in the System Y-Ta-O-N: A Nitrogen-Rich Analogue to Yttria-Stabilized Zirconia (YSZ). Zeitschrift für Naturforschung B 2014. [DOI: 10.1515/znb-2006-0604] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Fluorite-type phases in the system Y-Ta-O-N have been prepared by ammonolysis of Y-Ta-O precursors. X-ray powder patterns show unusual asymmetrical reflection profiles explained by DFT and MD methods. The anion vacancy concentration of some of these oxynitrides is similar to that of yttria-doped zirconia, commercially used as solid electrolyte in fuel cells. Hence, these compounds are interesting candidates for mixed oxygen-nitrogen superion conductors
Collapse
Affiliation(s)
- H. Schilling
- Institut für Chemie, TU Berlin, Straße des 17. Juni 135, D-10623 Berlin
| | - H. Wolff
- Institut für Anorganische Chemie, RWTH Aachen, Landoldtweg 1, D-52056 Aachen
| | - R. Dronskowski
- Institut für Anorganische Chemie, RWTH Aachen, Landoldtweg 1, D-52056 Aachen
| | - M. Lerch
- Institut für Anorganische Chemie, RWTH Aachen, Landoldtweg 1, D-52056 Aachen
| |
Collapse
|
9
|
Herlitschke M, Tchougréeff AL, Soudackov AV, Klobes B, Stork L, Dronskowski R, Hermann RP. Magnetism and lattice dynamics of FeNCN compared to FeO. NEW J CHEM 2014. [DOI: 10.1039/c4nj00097h] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Mössbauer spectra of FeNCN at 6 and 296 K reveal that, in contrast to the usual behaviour, the hyperfine magnetic field is reduced upon cooling.
Collapse
Affiliation(s)
- M. Herlitschke
- Jülich Centre for Neutron Science JCNS and Peter Grünberg Institute PGI
- JARA-FIT
- Forschungszentrum Jülich GmbH
- D-52425 Jülich, Germany
- Faculté des Sciences
| | - A. L. Tchougréeff
- Chair of Solid-State and Quantum Chemistry
- RWTH Aachen University
- D-52056 Aachen, Germany
- Independent University of Moscow
- Moscow Center for Continuous Mathematical Education
| | - A. V. Soudackov
- Department of Chemistry
- University of Illinois at Urbana-Champaign
- Urbana, USA
| | - B. Klobes
- Jülich Centre for Neutron Science JCNS and Peter Grünberg Institute PGI
- JARA-FIT
- Forschungszentrum Jülich GmbH
- D-52425 Jülich, Germany
| | - L. Stork
- Chair of Solid-State and Quantum Chemistry
- RWTH Aachen University
- D-52056 Aachen, Germany
| | - R. Dronskowski
- Chair of Solid-State and Quantum Chemistry
- RWTH Aachen University
- D-52056 Aachen, Germany
| | - R. P. Hermann
- Jülich Centre for Neutron Science JCNS and Peter Grünberg Institute PGI
- JARA-FIT
- Forschungszentrum Jülich GmbH
- D-52425 Jülich, Germany
- Faculté des Sciences
| |
Collapse
|
10
|
Abstract
We propose a new frustrated Heisenberg antiferromagnetic model with spatially anisotropic exchange parameters Jc, Ja, and Jac, extending along the c, a, and a ± c (c-a-ca model) lattice directions, and apply it to describe the fascinating physics of copper carbodiimide, CuNCN, assuming the resonating valence bond (RVB) type of its phases. This explains within a unified picture the intriguing absence of magnetic order in CuNCN. We further present a parameters-temperature phase diagram of the c-a-ca-RVB model in the high-temperature approximation. Eight different phases including Curie and Pauli paramagnets (respectively, in disordered and 1D- or Q1D-RVB phases) and (pseudo)gapped (quasi-Arrhenius) paramagnets (2D-RVB phases) are possible. By adding magnetostriction and elastic terms to the model, we derive possible structural manifestations of RVB phase transitions. Assuming a sequence of RVB phase transitions to occur in CuNCN with decreasing temperature, several anomalies observed in the temperature course of the lattice constants are explained.
Collapse
Affiliation(s)
- A L Tchougréeff
- Institut für anorganische Chemie RWTH-Aachen University, Landoltweg 1, D-52056, Aachen, Germany
| | | |
Collapse
|
11
|
|
12
|
Bolvardi H, Emmerlich J, to Baben M, Music D, von Appen J, Dronskowski R, Schneider JM. Systematic study on the electronic structure and mechanical properties of X2BC (X = Mo, Ti, V, Zr, Nb, Hf, Ta and W). J Phys Condens Matter 2013; 25:045501. [PMID: 23258257 DOI: 10.1088/0953-8984/25/4/045501] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In this work the electronic structure and mechanical properties of the phases X(2)BC with X =Ti, V, Zr, Nb, Mo, Hf, Ta, W (Mo(2)BC-prototype) were studied using ab initio calculations. As the valence electron concentration (VEC) per atom is increased by substitution of the transition metal X, the six very strong bonds between the transition metal and the carbon shift to lower energies relative to the Fermi level, thereby increasing the bulk modulus to values of up to 350 GPa, which corresponds to 93% of the value reported for c-BN. Systems with higher VEC appear to be ductile as inferred from both the more positive Cauchy pressure and the larger value of the bulk to shear modulus ratio (B/G). The more ductile behavior is a result of the more delocalized interatomic interactions due to larger orbital overlap in smaller unit cells. The calculated phase stabilities show an increasing trend as the VEC is decreased. This rather unusual combination of high stiffness and moderate ductility renders X(2)BC compounds with X = Ta, Mo and W as promising candidates for protection of cutting and forming tools.
Collapse
Affiliation(s)
- H Bolvardi
- Materials Chemistry, RWTH Aachen University, Kopernikusstraße 10, D-52074 Aachen, Germany.
| | | | | | | | | | | | | |
Collapse
|
13
|
Weber D, Wessel C, Reimann C, Schwickert C, Müller A, Ressler T, Pöttgen R, Bredow T, Dronskowski R, Lerch M. Anosovite-Type V3O5: A New Binary Oxide of Vanadium. Inorg Chem 2012; 51:8524-9. [DOI: 10.1021/ic301096d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- D. Weber
- Institut für Chemie,
TU Berlin, Straße des 17. Juni 135, D-10623 Berlin
| | - C. Wessel
- Institut für Anorganische
Chemie, RWTH Aachen University, Landoltweg 1, D-52056 Aachen
| | - C. Reimann
- Institut für Physikalische
und Theoretische Chemie, Universität Bonn, Wegelerstraße
12, D-53115 Bonn
| | - C. Schwickert
- Institut
für Anorganische
und Analytische Chemie, Universität Münster, Corrensstraße
30, D-48149 Münster
| | - A. Müller
- Institut für Chemie,
TU Berlin, Straße des 17. Juni 135, D-10623 Berlin
| | - T. Ressler
- Institut für Chemie,
TU Berlin, Straße des 17. Juni 135, D-10623 Berlin
| | - R. Pöttgen
- Institut
für Anorganische
und Analytische Chemie, Universität Münster, Corrensstraße
30, D-48149 Münster
| | - T. Bredow
- Institut für Physikalische
und Theoretische Chemie, Universität Bonn, Wegelerstraße
12, D-53115 Bonn
| | - R. Dronskowski
- Institut für Anorganische
Chemie, RWTH Aachen University, Landoltweg 1, D-52056 Aachen
| | | |
Collapse
|
14
|
Wessel C, Reimann C, Müller A, Weber D, Lerch M, Ressler T, Bredow T, Dronskowski R. Electronic structure and thermodynamics of V2O3 polymorphs. J Comput Chem 2012; 33:2102-7. [DOI: 10.1002/jcc.23046] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 05/23/2012] [Accepted: 05/24/2012] [Indexed: 11/09/2022]
|
15
|
Zorko A, Jeglič P, Potočnik A, Arčon D, Balčytis A, Jagličić Z, Liu X, Tchougréeff AL, Dronskowski R. Unconventional magnetism in a nitrogen-containing analog of cupric oxide. Phys Rev Lett 2011; 107:047208. [PMID: 21867041 DOI: 10.1103/physrevlett.107.047208] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 06/27/2011] [Indexed: 05/31/2023]
Abstract
We have investigated the magnetic properties of CuNCN, the first nitrogen-based analog of cupric oxide CuO. Our muon-spin relaxation, nuclear magnetic resonance, and electron-spin resonance studies reveal that classical magnetic ordering is absent down to the lowest temperatures. However, a large enhancement of spin correlations and an unexpected inhomogeneous magnetism have been observed below 80 K. We attribute this to a peculiar fragility of the electronic state against weak perturbations due to geometrical frustration, which selects between competing spin-liquid and more conventional frozen states.
Collapse
Affiliation(s)
- A Zorko
- Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Weber D, Stork A, Nakhal S, Wessel C, Reimann C, Hermes W, Müller A, Ressler T, Pöttgen R, Bredow T, Dronskowski R, Lerch M. Bixbyite-Type V2O3—A Metastable Polymorph of Vanadium Sesquioxide. Inorg Chem 2011; 50:6762-6. [DOI: 10.1021/ic200799n] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- D. Weber
- Institut für Chemie, TU Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| | - A. Stork
- Institut für Chemie, TU Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| | - S. Nakhal
- Institut für Chemie, TU Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| | - C. Wessel
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, D-52056 Aachen, Germany
| | - C. Reimann
- Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstrasse 12, D-53115 Bonn, Germany
| | - W. Hermes
- Institut für Anorganische und Analytische Chemie, Universität Münster, Corrensstrasse 30, D-48149 Münster, Germany
| | - A. Müller
- Institut für Chemie, TU Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| | - T. Ressler
- Institut für Chemie, TU Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| | - R. Pöttgen
- Institut für Anorganische und Analytische Chemie, Universität Münster, Corrensstrasse 30, D-48149 Münster, Germany
| | - T. Bredow
- Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstrasse 12, D-53115 Bonn, Germany
| | - R. Dronskowski
- Institut für Anorganische Chemie, RWTH Aachen University, Landoltweg 1, D-52056 Aachen, Germany
| | - M. Lerch
- Institut für Chemie, TU Berlin, Strasse des 17. Juni 135, D-10623 Berlin, Germany
| |
Collapse
|
17
|
Misse PRN, Dronskowski R, Fokwa BPT. Synthesis, Crystal Chemistry and Magnetism of the Metal-rich Borides MxRh7-xB3 (M = Cr, Mn, Ni; x = 0.39 - 1) with Th7Fe3-type Structure. Z Naturforsch B 2011. [DOI: 10.5560/znb.2011.66b1241] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
18
|
Hoepfner V, Englert U, Dronskowski R. Synthesis and Crystal Structure Determination of a Guanidine Adduct of Sodium Guanidinate, NaCN3H4(CN3H5)2. Z Naturforsch B 2011. [DOI: 10.5560/znb.2011.66b0975] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
19
|
|
20
|
Affiliation(s)
- A. L. Tchougréeff
- Poncelet Laboratory, Independent University of Moscow, Moscow Center for Continuous Mathematical Education, Bolshoy Vlasyevskiy Pereulok 11, 119002 Moscow, Russia
| | - A. M. Tokmachev
- JARA, Institut für Anorganische Chemie, RWTH Aachen, Landoltweg 1, 52056 Aachen, Germany
| | - R. Dronskowski
- JARA, Institut für Anorganische Chemie, RWTH Aachen, Landoltweg 1, 52056 Aachen, Germany
| |
Collapse
|
21
|
|
22
|
Schilling H, Irran E, Wolff H, Bredow T, Dronskowski R, Lerch M. γ-TaON: A New Metastable Polymorph of Tantalum Oxynitride. Z Anorg Allg Chem 2006. [DOI: 10.1002/zaac.200670119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
23
|
Fickenscher T, Rayaprol S, Pöttgen R, von Appen J, Dronskowski R, Łątka K, Gurgul J. Chemical Bonding, Magnetic and Spectroscopic Properties of GdRu2SiC. Z Anorg Allg Chem 2006. [DOI: 10.1002/zaac.200670075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
24
|
Schilling H, Lerch M, Börger A, Becker KD, Wolff H, Dronskowski R, Bredow T, Tovar M. Synthesis, Crystal Structure and High Temperature Behavior of an Anatase-Type Phase in the System Mg-Ta-O-N. Z Anorg Allg Chem 2006. [DOI: 10.1002/zaac.200670123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
25
|
Schilling H, Lerch M, Börger A, Becker KD, Wolff H, Dronskowski R, Bredow T, Tovar M, Baehtz C. A new anatase-type phase in the system Mg–Ta–O–N. J SOLID STATE CHEM 2006. [DOI: 10.1016/j.jssc.2006.04.036] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
26
|
Abstract
The electronic structure of a vast majority of molecular systems can be understood in terms of electron groups and their wave functions. They serve as a natural basis for bringing intuitive chemical and physical concepts into quantum chemical calculations. This article considers the general electron group functions formalism as well as its simple geminal version. We try to characterize the wave function with the group structure and its capabilities in actual calculations. For this purpose we implement a variational method based on the wave function in the form of an antisymmetrized product of strongly orthogonal group functions and perform a series of electronic structure calculations for small molecules and model systems. The most important point studied is the relation between the choice of electron groups and the results obtained. We consider energetic characteristics as well as optimal geometry parameters. In view of practical importance, the structure of variationally optimized local one-electron states is considered in detail as well as intuitive characteristics of chemical bonds.
Collapse
Affiliation(s)
- A M Tokmachev
- Institut für Anorganische Chemie, Rheinisch-Westfälische Technische Hochschule, Prof.-Pirlet-Str. 1, 52056 Aachen.
| | | |
Collapse
|
27
|
Zhang H, Fang L, Dronskowski R, Müller P, Yuan R. Some A6B5O18 cation-deficient perovskites in the BaO–La2O3–TiO2–Nb2O5 system. J SOLID STATE CHEM 2004. [DOI: 10.1016/j.jssc.2004.08.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
28
|
Keppler BK, Hopf H, Dronskowski R, Kröger M, Kula MR, Maier ME, Priesner C. Ein naturwissenschaftliches Literaturkarussell. Chemie. CHEM UNSERER ZEIT 2004. [DOI: 10.1002/ciuz.19920260512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
29
|
Ngaruiya JM, Kappertz O, Liesch C, M�ller P, Dronskowski R, Wuttig M. Composition and formation mechanism of zirconium oxynitride films produced by reactive direct current magnetron sputtering. ACTA ACUST UNITED AC 2004. [DOI: 10.1002/pssa.200306774] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
30
|
|
31
|
|
32
|
Dronskowski R, Liu X. Crystal structure of copper(II) tetracyanamide dichloride, Cu(NCNH2)4Cl2. Z KRIST-NEW CRYST ST 2002. [DOI: 10.1524/ncrs.2002.217.1.118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
33
|
Abstract
A chemical view of spin magnetic phenomena in finite (atoms and molecules) and infinite (transition metals and their alloys) systems using the concepts of bonding and electronic shielding is presented. The concept is intended to serve as a semiquantitative signpost for the synthesis of new ferromagnets. After a concise overview of the historic development of related theories developed within the physics community, the consequences of spin-spin coupling (made manifest in the exchange or Fermi hole) in atoms and molecules are explored. Upon moving to a paramagnetic state, the majority/minority spin species become more/less tightly bound to the nucleus, resulting in differences in the energies and spatial extents of the two sets of spin orbitals. By extrapolating well-known arguments from ligand-field theory, the paucity of ferromagnetic transition metals arises from quenching the paramagnetism of the free atoms due to strong interatomic interactions in the solid state. Critical valence electron concentrations in Fe, Co, and Ni, however, result in local electronic instabilities due to the population of antibonding states at the Fermi level varepsilon(F). Removal of these antibonding states from the vicinity of varepsilon(F) is the origin of ferromagnetism; in the pure metals this results in strengthening the chemical bonds. In the 4d and 5d transition metals, the valence d orbitals are too well shielded from the nucleus, so a transition to a ferromagnetic state does not result in sufficiently large changes to occur. Thus, the exceptional occurence of ferromagnetism only in the first transition series appears to parallel the special main-group chemistry of the first long period. A connection between ferromagnetism in the transition metals and Pearson's absolute hardness eta is easily established and shows that ferromagnetism appears only when eta<0.2 eV in the nonmagnetic calculation. As expected from the principle of maximum hardness, Fe, Co, and Ni all become harder upon moving to the more stable ferromagnetic state. Magnetism in intermetallic alloys follows the same path. Whether or not an alloy contains ferromagnetic elements, the presence of antibonding states at varepsilon(F) serves as a "fingerprint" to indicate a ferromagnetic instability. The differences in the sizes of the local magnetic moments on the constituent atoms of a ferromagnetic alloy can be understood in terms of the relative contributions to the density of states at varepsilon(F) in the nonmagnetic calculations. Appropriately parameterized, nonmagnetic, semi-empirical calculations can also be used to expose the ferromagnetic instability in elements and alloys. These techniques, which have become relatively commonplace, can be used to guide the synthetic chemist in search of new ferromagnetic materials.
Collapse
Affiliation(s)
- GA Landrum
- Institut für Anorganische Chemie Rheinisch-Westfälische Technische Hochschule Prof.-Pirlet-Strasse 1, 52056 Aachen (Germany)
| | | |
Collapse
|
34
|
Quadflieg J, Schölten M, Dronskowski R. Crystal structure of potassium tetrabromoindate(III), KInВг4. Z KRIST-NEW CRYST ST 1998. [DOI: 10.1524/ncrs.1998.213.14.245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
35
|
|
36
|
|