Aaltodoc Repository :: Browsing by Author "Kraus, Florian"

Browsing by Author "Kraus, Florian"

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A 1D Coordination Polymer of UF5 with HCN as a Ligand
(2017-01-05) Scheibe, Benjamin; Rudel, Stefan S.; Buchner, Magnus R.; Karttunen, Antti J.; Kraus, Florian; University of Marburg; Department of Chemistry; Department of Chemistry and Materials Science
β-Uranium(V) fluoride was reacted with liquid anhydrous hydrogen cyanide to obtain a 1D coordination polymer with the composition (Formula presented.) [UF5(HCN)2], (Formula presented.) [UF4/1F2/2- (HCN)2/1], revealed by single-crystal X-ray structure determination. The reaction system was furthermore studied by means of vibrational and NMR spectroscopy, as well as by quantum chemical calculations. The compound presents the first described polymeric HCN Lewis adduct and the first HCN adduct of a uranium fluoride.
Binary Lead Fluoride Pb3F8
(WILEY-V C H VERLAG GMBH, 2019-12-05) Deubner, H. Lars; Sachs, Malte; Bandemehr, Jascha; Ivlev, Sergei I.; Karttunen, Antti J.; Kachel, Stefan R.; Klein, Benedikt P.; Ruppenthal, Lukas; Schöniger, Maik; Krug, Claudio K.; Herritsch, Jan; Gottfried, J. Michael; Aman, Jamal N.M.; Schmedt auf der Günne, Jörn; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg; University of Siegen
The binary lead fluoride Pb3F8 was synthesized by the reaction of anhydrous HF with Pb3O4 or by the reaction of BrF3 with PbF2. The compound was characterized by single-crystal and powder X-ray diffraction, IR, Raman, and solid-state MAS 19F NMR spectroscopy, as well as thermogravimetric analysis, XP and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Solid-state quantum-chemical calculations are provided for the vibrational analyses and band assignments. The electronic band structure offers an inside view of the mixed valence compound.
[Br4F21]− - a unique molecular tetrahedral interhalogen ion containing a μ4-bridging fluorine atom surrounded by BrF5 molecules
(Royal Society of Chemistry, 2024-03-07) Möbs, Martin; Graubner, Tim; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
The reaction of [NMe4][BrF6] with an excess of BrF5 leads to the compound [NMe4][Br4F21]·BrF5. It features molecular [(μ4-F)(BrF5)4]− anions of tetrahedron-like shape containing central μ4-bridging F atoms coordinated by four BrF5 molecules. It is the most BrF5-rich fluoridobromate anion by mass. Quantum-chemical calculations showed that the μ4-F-Br bonds within the anion are essentially ionic in nature. The compound is the first example where F atoms bridge μ4-like neither to metal nor to hydrogen atoms. It was characterized by Raman spectroscopy and by single-crystal X-ray diffraction. The latter showed surprisingly that its crystal structure is related to the intermetallic half-Heusler compound and structure type MgAgAs.
A brief visit to the BeCl2/ZnCl2 system and the prediction of a new polymorph of ZnCl2
(Verlag der Zeitschrift fur Naturforschung, 2020-05) Deubner, H. Lars; Bandemehr, Jascha; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
Reactions of zinc chloride with beryllium chloride in the molar ratios of 1:1 and 3:2 at T = 300°C in sealed ampoules lead to the formation of the two compounds Be1- xZnxCl2 (x = 0.563(2) and 0.489(3), respectively). Their composition and crystal structures were evidenced by single crystal X-ray structure analysis. Both compounds crystallize isotypic to β-BeCl2 in the tetragonal space group I41/acd, No. 142, tI96, with a = 10.7548(1), c = 19.4656(5) Å, V = 2251.50(7) Å3, Z = 32 at T = 100 K for the first and a = 10.7511(3), c = 19.2335(10) Å, V = 2223.1(2) Å3, Z = 32 at T = 100 K for the second compound. The positions of the Be atoms are mixed-occupied by Zn atoms. The compounds were additionally characterized by powder X-ray diffraction and infrared spectroscopy. Plots according to Vegard's law allowed for extrapolation towards a neat ZnCl2 phase that would crystallize in the β-BeCl2 structure, which is the ZnI2 structure type. Quantum chemical calculations have confirmed that such a ZnCl2 modification would represent a true local minimum.
Bromine Pentafluoride BrF5, the Formation of [BrF6]− Salts, and the Stereochemical (In)activity of the Bromine Lone Pairs
(WILEY-VCH VERLAG, 2022-12-27) Möbs, Martin; Graubner, Tim; Eklund, Kim; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
BrF5 can be prepared by treating BrF3 with fluorine under UV light in the region of 300 to 400 nm at room temperature. It was analyzed by UV-Vis, NMR, IR and Raman spectroscopy. Its crystal structure was redetermined by X-ray diffraction, and its space group was corrected to Pnma. Quantum-chemical calculations were performed for the band assignment of the vibrational spectra. A monoclinic polymorph of BrF5 was quantum chemically predicted and then observed as its low-temperature modification in space group P21/c by single crystal X-ray diffraction. BrF5 reacts with the alkali metal fluorides AF (A=K, Rb) to form alkali metal hexafluoridobromates(V), A[BrF6] the crystal structures of which have been determined. Both compounds crystallize in the K[AsF6] structure type (R (Formula presented.), no. 148, hR24). For the species [BrF6]+, BrF5, [BrF6]−, and [IF6]−, the chemical bonds and lone pairs on the heavy atoms were investigated by means of intrinsic bond orbital analysis.
Coexistence of Two Different Distorted Octahedral [MnF6]3− Sites in K3[MnF6]: Manifestation in Spectroscopy and Magnetism
(WILEY-V C H VERLAG GMBH, 2021-07-07) Stoll, Christiane; Atanasov, Mihail; Bandemehr, Jascha; Neese, Frank; Pietzonka, Clemens; Kraus, Florian; Karttunen, Antti J.; Seibald, Markus; Heymann, Gunter; Huppertz, Hubert; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Innsbruck; Max Planck Institute for Coal Research; University of Marburg; Osram Opto Semiconductors GmbH
As a consequence of the static Jahn-Teller effect of the 5E ground state of MnIII in cubic structures with octahedral parent geometries, their octahedral coordination spheres become distorted. In the case of six fluorido ligands, [MnF6]3− anions with two longer and four shorter Mn−F bonds making elongated octahedra are usually observed. Herein, we report the synthesis of the compound K3[MnF6] through a high-temperature approach and its crystallization by a high-pressure/high-temperature route. The main structural motifs are two quasi-isolated, octahedron-like [MnF6]3− anions of quite different nature compared to that met in ideal octahedral MnIII Jahn-Teller systems. Owing to the internal electric field of Ci symmetry dominated by the next-neighbour K+ ions acting on the MnIII sites, both sites, the pseudo-rhombic (site 1) and the pseudo-tetragonally elongated (site 2) [MnF6]3− anions are present in K3[MnF6]. The compound was characterized by single-crystal and powder X-ray diffraction, and magnetometry as well as by FTIR, Raman, and ligand field spectroscopy. A theoretical interpretation of the electronic structure and molecular geometry of the two Mn sites in the lattice is given by using a vibronic coupling model with parameters adjusted from multireference ab-initio cluster calculations.
Complexes featuring a linear [N≡U≡N] core isoelectronic to the uranyl cation
(Nature Publishing Group, 2020-10-01) Rudel, Stefan S.; Deubner, H. Lars; Müller, Matthias; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
The aqueous chemistry of uranium is dominated by the linear uranyl cation [UO2]2+, yet the isoelectronic nitrogen-based analogue of this ubiquitous cation, molecular [UN2], has so far only been observed in an argon matrix. Here, we present three different complexes of [UN2] obtained by the reaction of the uranium pentahalides UCl5 or UBr5 with anhydrous liquid ammonia. The [UN2] moieties are linear, with the U atoms coordinated by five additional ligands (ammonia, chloride or bromide), resulting in a pentagonal bipyramidal coordination sphere that is also commonly adopted by the uranyl cation [UO2(L)5]2+ (L, ligand). In all three cases, the nitrido ligands are further coordinated through their lone pairs by the Lewis-acidic ligands [U(NH3)8]4+ to form almost linear, trinuclear complex cations. Those were characterized by single-crystal X-ray diffraction, Raman and infrared spectroscopy, 14N/15N isotope studies and quantum chemical calculations, which support the presence of two U≡N triple bonds within the [UN2] moieties. [Figure not available: see fulltext.]
A Computational Study on Closed-Shell Molecular Hexafluorides MF6 (M=S, Se, Te, Po, Xe, Rn, Cr, Mo, W, U) – Molecular Structure, Anharmonic Frequency Calculations, and Prediction of the NdF6 Molecule
(WILEY-VCH VERLAG, 2023-05-02) Graubner, Tim; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
Quantum chemical methods were used to study the molecular structure and anharmonic IR spectra of the experimentally known closed-shell molecular hexafluorides MF6 (M=S, Se, Te, Xe, Mo, W, U). First, the molecular structures and harmonic frequencies were investigated using Density Functional Theory (DFT) with all-electron basis sets and explicitly considering the influence of spin-orbit coupling. Second, anharmonic frequencies and IR intensities were calculated with the CCSD(T) coupled cluster method and compared, where available, with IR spectra recorded by us. These comparisons showed satisfactory results. The anharmonic IR spectra provide means for identifying experimentally too little studied or unknown MF6 molecules with M=Cr, Po, Rn. To the best of our knowledge, we predict the NdF6 molecule for the first time and show it to be a true local minimum on the potential energy surface. We used intrinsic bond orbital (IBO) analyses to characterize the bonding situation in comparison with the UF6 molecule.
The Crystal Structure of MnF3 Revisited
(WILEY-V C H VERLAG GMBH, 2020-07-15) Bandemehr, Jascha; Stoll, Christiane; Heymann, Gunter; Ivlev, Sergei I.; Karttunen, Antti J.; Conrad, Matthias; Huppertz, Hubert; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; Philipps-Universität Marburg; Universität Innsbruck
We correct the crystal structure of MnF 3, of which the space group was reported as monoclinic C2/c (no. 15) with a = 8.9202, b = 5.0472, c = 13.4748 Å, β = 92.64°, V = 606.02 Å³, Z = 12, mS48, T not given, likely 298 K. In the structure model proposed here, we use a unit cell of one third of the former volume. The ruby red crystals of MnF 3 were synthesized by a high-pressure/high-temperature method, where MnF 4 was used as a starting material. As determined on a single crystal, MnF 3 crystallizes in the monoclinic space group I2/a (no. 15) with a = 5.4964(11), b = 5.0084(10), c = 7.2411(14) Å, β = 93.00(3)°, V = 199.06(7) Å 3, Z = 4, mS16, T = 183(2) K. The crystal structure of MnF 3 is related by a direct group-subgroup transition to the VF 3 structure-type. We performed quantum chemical calculations on the crystal structure to allow the assignment of bands of the obtained vibrational spectra.
The Crystal Structures of α- and β-F 2 Revisited
(WILEY-V C H VERLAG GMBH, 2019-01-01) Ivlev, Sergei I.; Karttunen, Antti J.; Hoelzel, Markus; Conrad, Matthias; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg; Technische Universität München
The crystal structures of α-F 2 and β-F 2 have been reinvestigated using neutron powder diffraction. For the low-temperature phase α-F 2 , which is stable below circa 45.6 K, the monoclinic space group C2/c with lattice parameters a=5.4780(12), b=3.2701(7), c=7.2651(17) Å, β=102.088(18)°, V=127.26(5) Å 3 , mS8, Z=4 at 10 K can now be confirmed. The structure model was significantly improved, allowed for the anisotropic refinement of the F atom, and an F−F bond length of 1.404(12) Å was obtained, which is in excellent agreement with spectroscopic data and high-level quantum chemical predictions. The high-temperature phase β-F 2 , stable between circa 45.6 K and the melting point of 53.53 K, crystallizes in the cubic primitive space group Pm (Formula presented.) n with the lattice parameter a=6.5314(15) Å, V=278.62(11) Å 3 , cP16, Z=8, at 48 K. β-F 2 is isotypic to γ-O 2 and δ-N 2 . The centres of gravity of the F 2 molecules are arranged like the atoms in the Cr 3 Si structure type.
Crystal Structures of α- And β-Nitrogen Trifluoride
(American Chemical Society ACS, 2019-05-06) Ivlev, Sergei I.; Conrad, Matthias; Hoelzel, Markus; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg; Technische Universität München
The crystal structures of α-NF 3 and β-NF 3 are reported for the first time. As shown by powder neutron diffraction, the lowerature α-NF 3 crystallizes in the orthorhombic space group Pnma (oP16) with lattice parameters a = 6.71457(13) Å, b = 7.30913(14) Å, c = 4.55189(8) Å, V = 223.396(7) Å 3 , and Z = 4 at T = 6 K. The intramolecular atom distances in α-NF 3 are 1.3639(16) and 1.3677(11) Å for N-F, and 2.1216(16) and 2.120(2) Å for F···F. The F-N-F bond angles are 101.92(7)° and 101.63(10)°. All data are in excellent agreement with quantum-chemical predictions and previously reported experimentally obtained gas-phase data. The higherature β-NF 3 is a plastic crystal, space group P4 2 /mnm (tP120), with the lattice parameters a = 15.334(6) Å, c = 7.820(3) Å, V = 1838.6(12) Å 3 , and Z = 30 at T = 60 K. Its crystal structure is closely related to that of the Frank-Kasper sigma phase.
Cs[Cl3F10] : A Propeller-Shaped [Cl3F10]− Anion in a Peculiar A[5]B[5] Structure Type
(WILEY-V C H VERLAG GMBH, 2020-10-05) Scheibe, Benjamin; Karttunen, Antti J.; Müller, Ulrich; Kraus, Florian; University of Marburg; Department of Chemistry and Materials Science
Reaction of CsF with ClF3 leads to Cs[Cl3F10]. It contains a molecular, propeller-shaped [Cl3F10]− anion with a central μ3-F atom and three T-shaped ClF3 molecules coordinated to it. This anion represents the first example of a heteropolyhalide anion of higher ClF3 content than [ClF4]− and is the first Cl-containing interhalogen species with a μ-bridging F atom. The chemical bonds to the central μ3-F atom are highly ionic and quite weak as the bond lengths within the coordinating XF3 units (X = Cl, and also calculated for Br, I) are almost unchanged in comparison to free XF3 molecules. Cs[Cl3F10] crystallizes in a very rarely observed A[5]B[5] structure type, where cations and anions are each pseudohexagonally close packed, and reside, each with coordination number five, in the trigonal bipyramidal voids of the other.
DFT-Guided Crystal Structure Redetermination and Lattice Dynamics of the Intermetallic Actinoid Compound UIr
(AMERICAN CHEMICAL SOCIETY, 2021-11-01) Sachs, Malte; Ivlev, Sergei I.; Etter, Martin; Conrad, Matthias; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg; Deutsches Elektronen-Synchrotron
UIr has been discussed as a rare example of a noncentrosymmetric, ferromagnetic superconductor crystallizing in the acentric PdBi structure type (P21, mP16). Here we present a new structure model for UIr. By means of single-crystal and powder X-ray diffraction we find UIr to crystallize in the centrosymmetric space group P21/c, in line with previous ab initio calculations. The discrepancy with the previous noncentrosymmetric model in space group P21 is explained by the occurrence of twinning. The observed twinning hints toward a high-temperature displacive phase transition of UIr to the CrB structure type (Cmcm, oS8): we discuss the lattice dynamics corresponding to this transition by crystallographic symmetry mode analysis and by density functional theory (DFT). We find that spin-orbit coupling is essential to understand this phase transition. We apply our theoretical considerations for a critical judgment of the structure models of UPt and NpIr that have been reported to crystallize isotypically with UIr. We confirm that UPt is isotypic to UIr (P21/c), whereas we predict NpIr to crystallize in the CrB structure type. Our report on the centrosymmetric crystal structure of UIr has an effect on all those theoretical models that investigated potentially novel superconducting coupling mechanisms of this compound on the basis of the noncentrosymmetric structure model.
Difluorochloronium(III) Fluoridometallates - from Molecular Building Blocks to (Helical) Chains
(WILEY-BLACKWELL, 2020-12-20) Scheibe, Benjamin; Haiges, Ralf; Ivlev, Sergei I.; Karttunen, Antti J.; Müller, Ulrich; Christe, Karl O.; Kraus, Florian; University of Marburg; University of Southern California; Inorganic Materials Modelling; Department of Chemistry and Materials Science
Difluorochloronium(III) compounds were synthesized from the reaction of metal powders (Ru, Os, Ir, Au), metal fluorides (NbF5, SbF3, BiF5) or a metal chloride (TaCl5) with excess liquid chlorine trifluoride. The compounds ClF2[AuF4], ClF2[MF6] (M = Nb, Ta, Ru, Os, Ir, Sb, Bi) and ClF2[Ta2F11] were obtained in crystalline form and their crystal structures were determined by single-crystal X-ray diffraction. The ClF2+ cations in the investigated compounds are bent, containing two strong, short, mainly covalent Cl-F bonds and two sterically active, free valence electron pairs in a pseudo-tetrahedral arrangement. The coordination around the Cl atom is extended by two highly ionic, long fluorine bridges to neighboring fluoridometallate anions, resulting in a total coordination number of six. The crystal structures vary among the ClF2+ compounds and range from molecular building blocks, such as dimeric (ClF2[AuF4])(2) and (ClF2[Ta2F11])(2), to chains, some of which being helical, as in ClF2[MF6], (M = Nb, Ta, Ru, Os, Ir, Sb, Bi). Quantum-chemical solid-state and gas-phase calculations were carried out to elucidate the bonding within the ClF2+ cations and their interactions with the bridging F atoms.
A Dinuclear Uranium Complex [{UO2F2(NH3)}2(μ-F)2]2− from Reaction of TlF and UO2F2 in Liquid Anhydrous Ammonia and Fluoride Ion Affinities for Some Uranyl(VI) Species [UO2Fx]2−x and [UO2Fx(NH3)5−x]2−x
(Wiley-VCH Verlag, 2023-10-02) Graubner, Tim; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
UO2F2 abstracts F− anions from TlF in liquid ammonia solution and the compound [Tl2(NH3)6][{UO2F2(NH3)}2(μ-F)2] is formed. The compound has been characterized by single crystal X-ray diffraction, Raman spectroscopy and quantum-chemical calculations for the solid state. Quantum-chemical investigation of the [{UO2F2(NH3)}2(μ-F)2]2− anion showed that the U−(μ-F)−U σ-3c-4e-bond is essentially ionic. The [Tl2(NH3)6]2+ cation shows a thallophilic Tl⋅⋅⋅Tl interaction. Fluoride ion affinities (FIAs) were calculated for different UO22+ species [UO2Fx]2−x and [UO2Fx(NH3)5−x]2−x with x=0 to 4.
Discrete Mono-, Di-, and Trinuclear Anions [MoOF5]−, [MoVOF5]2-, [MoO2F4]2-, [Mo2O2F9]−, [Mo3O3F13]−, and the Infinite Chain Anion [MoO2F3]− Obtained from Reactions of MoOF4: Synthesis and Analysis of the Structure-Chemical Relations of the Compounds
(American Chemical Society, 2023-08-21) Wassermann, Tobias B.; Stene, Riane E.; Scheibe, Benjamin; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
The herein-reported oxyfluoridometallate salts were synthesized and structurally characterized during the studies of the Lewis acidity of MOF4 (M = Mo, W) with various fluoride ion donors (RbF, CsF, TlF, AgF, SrF2, BaF2, PbF2) in different solvents (aqHF 48%, aHF, BrF3, ClF3). Phase-pure MoOF4 was either synthesized by hydrolysis of MoF6 with SiO2 in anhydrous HF (aHF) or by reactions of BrF3 with MoO2 or MoO3, respectively. The compound was characterized by infrared and Raman spectroscopy, solid-state quantum-chemical calculations, as well as powder and single-crystal X-ray diffraction. MoOF4 reacted with PbF2 in aHF forming Pb[MoOF5]2, while under comparable conditions, WOF4 formed Pb3[WOF5]4F2, containing the [WOF5]− anion. Salts containing such [MoOF5]− anions were also directly obtained from reactions of BrF3, MoO3, and AF2 (A = Sr, Ba), while with AgF, the compound Ag[Mo2O2F9] was observed. ClF3 reacted with MoO3 to form [ClOF2][Mo3O3F13]. Carrying out similar reactions in aqueous HF (aqHF) in autoclaves under hydrofluorothermal conditions leads to O-richer compounds with the composition A[MoO2F4] (A = Sr, Ba). With RbF or Tl2(CO3), the compounds A[MoO2F3] (A = Rb, Tl) were obtained. With CsF reduction to Mo(V) occurred as Cs2[MoVOF5] was formed. We report on similarities and differences within the respective anions and within the crystal structures of these compounds.
Evolutionary Algorithm-Based Crystal Structure Prediction for Copper (I) Fluoride
(WILEY-V C H VERLAG GMBH, 2019-09-02) Kuklin, Mikhail; Maschio, Lorenzo; Usvyat, Denis; Kraus, Florian; Karttunen, Antti; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Turin; Humboldt-Universität zu Berlin; University of Marburg
Despite numerous experimental studies since 1824, the binary copper(I) fluoride remains unknown. A crystal structure prediction has been carried out for CuF using the USPEX evolutionary algorithm and a dispersion‐corrected hybrid density functional method. In total about 5000 hypothetical structures were investigated. The energetics of the predicted structures were also counter‐checked with local second‐order Møller–Plesset perturbation theory. Herein 39 new hypothetical copper(I) fluoride structures are reported that are lower in energy compared to the previously predicted cinnabar‐type structure. Cuprophilic Cu−Cu interactions are present in all the low‐energy structures, leading to ordered Cu substructures such as helical or zig‐zag‐type Cu−Cu motifs. The lowest‐energy structure adopts a trigonal crystal structure with space group P3121. From an electronic point of view, the predicted CuF modification is a semiconductor with an indirect band gap of 2.3 eV.
Evolutionary Algorithm-based Crystal Structure Prediction for Gold(I) Fluoride
(WILEY-V C H VERLAG GMBH, 2020-04-20) Eklund, Kim; Kuklin, Mikhail S.; Kraus, Florian; Karttunen, Antti J.; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
Solid gold(I) fluoride remains as an unsynthesized and uncharacterized compound. We have performed a search for potential gold(I) fluoride crystal structures using USPEX evolutionary algorithm and dispersion-corrected hybrid density functional methods. Over 4000 AuF crystal structures have been investigated. Behavior of the AuF crystal structures under pressure was studied up to 25 GPa, and we also evaluated the thermodynamic stability of the hypothetical AuF crystal structures with respect to AuF3, AuF5, and Au3F8. Mixed-valence compound Au3[AuF4] with Au atoms in various formal oxidation states emerged as the thermodynamically most stable AuF species.
The Fluoroperovskite TlMnF3
(WILEY-V C H VERLAG GMBH, 2018) Conrad, Matthias; Pietzonka, Clemens; Bernzen, Janek; Motta, Viviana; Weitzel, Karl Michael; Karttunen, Antti J.; Kraus, Florian; Department of Chemistry and Materials Science; Inorganic Materials Modelling; University of Marburg
TlMnF3 was obtained from the reduction of Tl3MnF6 under liquid ammonia, in which MnIII is obviously not redox-stable under the applied conditions. The crystal structure of TlMnF3 was determined on a single crystal using X-ray diffraction. The previously reported structure model was deduced from powder X-ray diffraction data only and therefore a much higher precision has been reached now. The compound crystallizes in the shape of colorless cubes with lattice parameters a = 4.2370(4) Å, V = 76.06(2) Å3 with Z = 1 at T = 140 K in the perovskite structure type (Pm3m, no. 221). At room temperature (T = 293 K), the lattice parameter of the slightly pink, almost colorless powderous compound is a = 4.2535(2) Å, V = 76.953(4) Å3. As the displacement parameter of the Tl atom was observed being rather large in comparison to the other atoms, the CAIT technique was used to demonstrate the mobility of the Tl cations. Additionally, quantum chemical calculations were carried out to further investigate the behavior of the Tl atoms. We calculate that most of the Tl atoms vibrate already at 75 K. Magnetic measurements showed that TlMnF3 is an antiferromagnet with TN = 82 K and a Weiss temperature θ of –151.2(2) K.
A Fresh Look at a Well-Known Solid: Structure, Vibrational Spectra, and Formation Energy of NaNH2
(American Chemical Society, 2023-06-29) Bonometti, Laura; Kraus, Florian; Graubner, Tim; Karttunen, Antti J.; Civalleri, Bartolomeo; Donà, Lorenzo; Maschio, Lorenzo; University of Turin; University of Marburg; Department of Chemistry and Materials Science; Department of Chemistry and Materials Science
Sodium amide (NaNH2) in its α form is a common compound that has recently seen renewed interest, mainly for its potential use as a solid-state hydrogen storage material. In this work, we present a synergic theoretical and experimental characterization of the compound, including novel measured and simulated vibrational spectra (IR and Raman) and X-ray diffraction patterns. We put forward the hypothesis of a low-temperature symmetry breaking of the structure to space group C2/c, while space group Fddd is commonly reported in the literature and experimentally found down to 80 K. Additionally, we report a theoretical estimate of the heat of formation of sodium amide from ammonia to be equal to -12.2 kcal/mol at ambient conditions.

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