Marcus Tegel

Publications

• 11.83

  Impact points

  Superconductivity up to 35 K in the iron platinum arsenides (CaFe(1-x)Pt(x)As)10Pt(4-y)As8 with layered structures.

  Catrin Löhnert, Tobias Stürzer, Marcus Tegel, Rainer Frankovsky, Gina Friederichs, Dirk Johrendt

  Angewandte Chemie (International ed. in English). 09/2011; 50(39):9195-9.

• Superconductivity up to 35 K in the iron-platinum arsenides (CaFe1-xPtxAs)10Pt4-yAs8 with layered structures

  Catrin Löhnert, Tobias Stürzer, Marcus Tegel, Rainer Frankovsky, Gina Friederichs, Dirk Johrendt

  07/2011;

  We report the synthesis and crystal structures of three new superconducting iron-platinum arsenides (CaFe1-xPtxAs)10Pt4-yAs8 (x = 0-0.15, y = 0-0.4). The structures are stacking variants of FeAs- and slightly puckered Pt4-yAs8-layers with square coordinated platinum separated by calcium-layers, resp... [more] We report the synthesis and crystal structures of three new superconducting iron-platinum arsenides (CaFe1-xPtxAs)10Pt4-yAs8 (x = 0-0.15, y = 0-0.4). The structures are stacking variants of FeAs- and slightly puckered Pt4-yAs8-layers with square coordinated platinum separated by calcium-layers, respectively. Arsenic atoms in the Pt4-yAs8-layers form (As2)4- dumbbells according to Zintl's concept, providing charge balance in (Ca2+Fe2+As3-)10(Pt2+)3[(As2)4-]4. Superconductivity was observed at 13-35 K. We suggest that the highest Tc above 30 K occurs in the 1048 phase with clean FeAs-layers that are indirectly electron-doped according to (Ca2+Fe2+As3-)10(Pt2+)4[(As2)4-]4*2e-. We also suggest that the lower critical temperatures occur in the 1038- and a-1048 phases due to Pt-doping at the Fe-site. DFT band structure calculations indicate that the contribution of the Pt4-yAs8-layers to the Fermi surface is small and that the Fermi energy is slightly either below or above a quasi-gap in the Pt-states. The new platinum-iron compounds represent the first iron-based superconductors with so far unknown structure types and can serve as a new platform for further studies that go beyond the known systems.

• Suppression of superconductivity by V-doping and possible magnetic order in Sr2VO3FeAs

  Marcus Tegel, Tanja Schmid, Tobias Stürzer, Masamitsu Egawa, Yixi Su, Anatoliy Senyshyn, Dirk Johrendt

  08/2010;

  Superconductivity at 33 K in Sr2VO3FeAs is completely suppressed by small amounts of V-doping in Sr2VO3[Fe0.93(+/-0.01)V0.07(+/-0.01)]As. The crystal structures and exact stoichiometries are determined by combined neutron- and x-ray powder diffraction. Sr2VO3FeAs is shown to be very sensitive to Fe/... [more] Superconductivity at 33 K in Sr2VO3FeAs is completely suppressed by small amounts of V-doping in Sr2VO3[Fe0.93(+/-0.01)V0.07(+/-0.01)]As. The crystal structures and exact stoichiometries are determined by combined neutron- and x-ray powder diffraction. Sr2VO3FeAs is shown to be very sensitive to Fe/V mixing, which interferes with or even suppresses superconductivity. This inhomogeneity may be intrinsic and explains scattered reports regarding Tc and reduced superconducting phase fractions in Sr2VO3FeAs. Neutron diffraction data collected at 4 K indicates incommensurate mag- netic ordering of the V-sublattice with a propagation vector q = (0,0,0.306). This suggests strongly correlated vanadium, which does not contribute significantly to the Fermi surface of Sr2VO3FeAs. Comment: text revised, magnetic q-vector added, one reference added 4 pages, 4 figures

• Polymorphism of isotypic series of homoleptic 1,2,3-triazolate MOFs [Ln(Tz*)(3)] containing the heavy lanthanides Gd-Lu: from open to dense frameworks of varying dimensionality

  JC RYBAK, M TEGEL, D JOHRENDT, K MÜLLER-BUSCHBAUM

  Zeitschrift Für Kristallographie. 01/2010; 225:187-194.

• The crystal structure of FeSe0.44Te0.56

  Marcus Tegel, Catrin Loehnert, Dirk Johrendt

  12/2009;

  The crystal structure of the superconductor FeSe0.44Te0.56 was redetermined by high-resolution X-ray single crystal diffraction at 173 K (anti-PbO-type, P4/nmm, a=3.7996(2), c=5.9895(6) A, R1=0.022, wR2=0.041, 173 F^2). Significantly different z-coordinates of tellurium and selenium at the 2c site a... [more] The crystal structure of the superconductor FeSe0.44Te0.56 was redetermined by high-resolution X-ray single crystal diffraction at 173 K (anti-PbO-type, P4/nmm, a=3.7996(2), c=5.9895(6) A, R1=0.022, wR2=0.041, 173 F^2). Significantly different z-coordinates of tellurium and selenium at the 2c site are clearly discernible and were refined to z_Te=0.2868(3) and z_Se=0.2468(7). Thus the chalcogen heights differ by 0.24 A and the Fe-Se bonds are by 0.154 A shorter than the Fe-Te bonds, while three independent (Te,Se)-Fe-(Te,Se) bond angles occur. An elevated U33 displacement parameter of the iron atom is suggestive of a slightly puckered Fe layer resulting from different combinations of Se or Te neighbors. Such strong disorder underlines the robustness of superconductivity against structural randomness and has not yet been considered in theoretical studies of this system. Comment: 9 pages, 2 figures, 3 tables

• Non-stoichiometry and the magnetic structure of Sr2CrO3FeAs

  Marcus Tegel, Franziska Hummel, Yixi Su, Tapan Chatterji, Michela Brunelli, Dirk Johrendt

  11/2009;

  The iron arsenide Sr2CrO3FeAs with the tetragonal Sr2GaO3CuS-type structure was synthesized and its crystal structure re-determined by neutron powder diffraction. In contrast to previous X-ray crystallographic studies, a mixed occupancy of chromium and iron was found within the FeAs4/4 layer (93+/-1... [more] The iron arsenide Sr2CrO3FeAs with the tetragonal Sr2GaO3CuS-type structure was synthesized and its crystal structure re-determined by neutron powder diffraction. In contrast to previous X-ray crystallographic studies, a mixed occupancy of chromium and iron was found within the FeAs4/4 layer (93+/-1% Fe : 7+/-1% Cr). We suggest that the partial Cr-doping at the Fe site is the reason for the absence of a spin-density wave anomaly and superconductivity in this compound. Additional experiments via neutron polarization analysis revealed short-range spin correlations below ~100 K and long-range antiferromagnetic ordering below T_N = 36 K with a magnetic propagation vector of q = (1/2, 1/2, 0). The Cr3+ ions form a collinear magnetic structure of the C-type in the magnetic space group C_Pmma' (a' = a-b, b'=a+b, c'=c), where Cr3+-ions occupy the 4g (0, 1/4, z) Wyckoff position. The magnetic moments are aligned along the orthorhombic a'-axis. At 3.5 K, an ordered magnetic moment of 2.75+/-0.05 mu_B for the Cr3+-sublattice was refined. Comment: 6 pages, 6 figures

• Low Temperature Crystal Structure and 57Fe Moessbauer Spectroscopy of Sr3Sc2O5Fe2As2

  Marcus Tegel, Inga Schellenberg, Franziska Hummel, Rainer Poettgen, Dirk Johrendt

  05/2009;

  The crystal structure of the layered iron arsenide Sr3Sc2O5Fe2As2 was determined between 300 and 10 K. The lattice parameters of the tetragonal cell decrease anisotropically according to delta(c)/c : delta(a)/a = 4.2, which results in a slight flattening of the As-Fe-As bond angle within the FeAs la... [more] The crystal structure of the layered iron arsenide Sr3Sc2O5Fe2As2 was determined between 300 and 10 K. The lattice parameters of the tetragonal cell decrease anisotropically according to delta(c)/c : delta(a)/a = 4.2, which results in a slight flattening of the As-Fe-As bond angle within the FeAs layers. No indication of a structural instability could be detected. 57Fe Moessbauer spectroscopic data show a single signal at 4.2, 77, and 298 K, respectively, subjected to quadrupole splitting. The isomer shift increases from 0.36(1) mm/s at 298 K to 0.49(1) mm/s at 4.2 K. No indication for magnetic ordering was found. Comment: 12 pages, 4 figures

• The layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs

  Marcus Tegel, Franziska Hummel, Sebastian Lackner, Inga Schellenberg, Rainer Poettgen, Dirk Johrendt

  04/2009;

  Polycrystalline samples of the layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs were synthesized by high temperature solid state reactions and their crystal structures determined by the X-ray powder diffraction. Their structures are tetragonal (P4/nmm; Sr2CrO3FeAs: a = 391.12(1) pm, c = 1579.05(3)... [more] Polycrystalline samples of the layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs were synthesized by high temperature solid state reactions and their crystal structures determined by the X-ray powder diffraction. Their structures are tetragonal (P4/nmm; Sr2CrO3FeAs: a = 391.12(1) pm, c = 1579.05(3) pm; Ba2ScO3FeAs: a = 412.66(5) pm, c = 1680.0(2) pm, Z = 2) and isotypic to Sr2ScO3CuS. Iron arsenide layers are sandwiched between perowskite-like oxide blocks and separated by ~1600 pm, which is much larger compared to the 1111 iron arsenide superconductors. The bond length and angles within the FeAs layers are adapted to the space requirements of the oxide blocks. Measurements of the magnetic susceptibility and electrical resistivity show no hint for a SDW-like anomaly in both compounds. Sr2CrO3FeAs shows Curie-Weiss paramagnetism above 160 K with an effective magnetic moment of 3.83(3) muB in good agreement with the theoretical value of 3.87 muB for Cr3+. Antiferromagnetic ordering was detected below TN ~ 31 K. 57Fe Moessbauer spectra of Sr2CrO3FeAs show a single signal that broadens below the magnetic ordering temperature due to a small transferred hyperfine field induced by the magnetic ordering of the chromium atoms. 57Fe-Moessbauer spectra of Ba2ScO3FeAs show single signals at 298, 77, and 4.2 K which are only subject to weak quadrupole splitting. Comment: substantial addititions and corrections, references updated 19 pages, 7 figures

• Competition of magnetism and superconductivity in underdoped (Ba1-xKx)Fe2As2

  Marianne Rotter, Marcus Tegel, Inga Schellenberg, Falko M. Schappacher, Rainer Poettgen, Joachim Deisenhofer, Axel Guenther, Florian Schrettle, Alois Loidl, Dirk Johrendt

  01/2009;

  Polycrystalline samples of underdoped (Ba1-xKx)Fe2As2 (x<=0.4) were synthesized and studied by x-ray powder diffraction, magnetic susceptibility, specific heat and 57Fe-Moessbauer-spectroscopy. The structural phase transition from tetragonal to orthorhombic lattice symmetry shifts towards lower t... [more] Polycrystalline samples of underdoped (Ba1-xKx)Fe2As2 (x<=0.4) were synthesized and studied by x-ray powder diffraction, magnetic susceptibility, specific heat and 57Fe-Moessbauer-spectroscopy. The structural phase transition from tetragonal to orthorhombic lattice symmetry shifts towards lower temperatures, becomes less pronounced at x = 0.1-0.2 and is no longer present at x = 0.3. Bulk superconductivity is observed in all samples except (Ba0.9K0.1)Fe2As2 by resistivity and magnetic susceptibility measurements. Specific heat data show a broad SDW phase transition in (Ba0.9K0.1)Fe2As2, which is hardly discernible in (Ba0.8K0.2)Fe2As2. No SDW anomaly is found in the specific heat of optimally doped (Ba0.6K0.4)Fe2As2, where C changes by 0.1 J/K at Tc = 37.3 K. 57Fe-Moessbauer-spectra show full magnetic hyperfine field splitting, indicative of antiferromagnetic ordering at 4.2 K in samples with x = 0-0.2, but zero magnetic hyperfine field in samples with x = 0.3. The spectra of (Ba0.9K0.1)Fe2As2 and (Ba0.8K0.2)Fe2As2 in the phase transition regions are temperature-dependent superpositions of magnetic and non-magnetic components, caused by inhomogeneous potassium distribution. Our results suggest the co-existence of AF magnetic ordering and superconductivity without mesoscopic phase separation in the underdoped region and show unambiguously homogeneous superconducting phases close to optimal doping. This is in contrast to recently reported results about single crystal (Ba1-xKx)Fe2As2.
• 7.33

  Impact points

  Superconductivity at 38 K in the Iron Arsenide (Ba1-xKx)Fe2As2.

  Marianne Rotter, Marcus Tegel, Dirk Johrendt

  Physical review letters. 10/2008; 101(10):107006.

  The ternary iron arsenide BaFe2As2 becomes superconducting by hole doping, which was achieved by partial substitution of the barium site with potassium. We have discovered bulk superconductivity at T_{c}=38 K in (Ba1-xKx)Fe2As2 with x approximately 0.4. The parent compound BaFe2As2 crystallizes in t... [more] The ternary iron arsenide BaFe2As2 becomes superconducting by hole doping, which was achieved by partial substitution of the barium site with potassium. We have discovered bulk superconductivity at T_{c}=38 K in (Ba1-xKx)Fe2As2 with x approximately 0.4. The parent compound BaFe2As2 crystallizes in the tetragonal ThCr2Si2-type structure, which consists of (FeAs);{delta-} iron arsenide layers separated by Ba2+ ions. BaFe2As2 is a poor metal and exhibits a spin density wave anomaly at 140 K. By substituting Ba2+ for K+ ions we have introduced holes in the (FeAs);{-} layers, which suppress the anomaly and induce superconductivity. The T_{c} of 38 K in (Ba0.6K0.4)Fe2As2 is the highest in hole doped iron arsenide superconductors so far. Therefore, we were able to expand this class of superconductors by oxygen-free compounds with the ThCr2Si2-type structure.
• 11.83

  Impact points

  Superconductivity and Crystal Structures of (Ba(1-x)K(x))Fe(2)As(2) (x=0-1).

  Marianne Rotter, Michael Pangerl, Marcus Tegel, Dirk Johrendt

  Angewandte Chemie (International ed. in English). 10/2008;

• Superconductivity and Crystal Structures of (Ba1-xKx)Fe2As2 (x = 0 - 1)

  Marianne Rotter, Michael Pangerl, Marcus Tegel, Dirk Johrendt

  08/2008;

  We report on doping dependencies of structural parameters and superconducting transition temperatures in the solid solution (Ba1-xKx)Fe2As2. As the main effect of doping on the crystal structure, we find linear decreasing As-Fe-As bond angles and Fe-Fe distances, equivalent to an elongation of the F... [more] We report on doping dependencies of structural parameters and superconducting transition temperatures in the solid solution (Ba1-xKx)Fe2As2. As the main effect of doping on the crystal structure, we find linear decreasing As-Fe-As bond angles and Fe-Fe distances, equivalent to an elongation of the FeAs4 tetrahedra along [001]. The structural changes are intimately coupled to the electronic states at the Fermi level, because the most relevant Fe-3dx2-y2 orbitals are strongly affected by the As-Fe-As bond angle. Superconductivity is present over the whole doping range in (Ba1-xKx)Fe2As2 with a maximum Tc of 38 K at x ~ 0.4. The superconducting transitions in the orthorhombic compounds (Ba0.9K0.1)Fe2As2 (Tc ~ 3 K) and (Ba0.8K0.2)Fe2As2 (Tc ~ 25 K) is strong evidence for the coexistence of superconductivity with the structurally distorted and potentially magnetically ordered state in the BaFe2As2 family of iron arsenide superconductors.

• Structural and magnetic phase transitions in the ternary iron arsenides SrFe2As2 and EuFe2As2

  Marcus Tegel, Marianne Rotter, Veronika Weiss, Falko M. Schappacher, Rainer Poettgen, Dirk Johrendt

  07/2008;

  The structural and magnetic phase transitions of the ternary iron arsenides SrFe2As2 and EuFe2As2 were studied by temperature-dependent x-ray powder diffraction and 57-Fe Moessbauer spectroscopy. Both compounds crystallize in the tetragonal ThCr2Si2-type structure at room temperature and exhibit dis... [more] The structural and magnetic phase transitions of the ternary iron arsenides SrFe2As2 and EuFe2As2 were studied by temperature-dependent x-ray powder diffraction and 57-Fe Moessbauer spectroscopy. Both compounds crystallize in the tetragonal ThCr2Si2-type structure at room temperature and exhibit displacive structural transitions at 203 K (SrFe2As2) or 190 K (EuFe2As2) to orthorhombic lattice symmetry in agreement with the group-subgroup relationship between I4/mmm and Fmmm. 57-Fe Moessbauer spectroscopy experiments with SrFe2 As2 show full hyperfine field splitting below the phase transition temperature (8.91(1) T at 4.2 K). Order parameters were extracted from detailed measurements of the lattice parameters and fitted to a simple power law. We find a relation between the critical exponents and the transition temperatures for AFe2As2 compounds, which shows that the transition of BaFe2As2 is indeed more continuous than the transition of SrFe2As2 but it remains second order even in the latter case.

• Spin density wave anomaly at 140 K in the ternary iron arsenide BaFe2As2

  Marianne Rotter, Marcus Tegel, Inga Schellenberg, Wilfried Hermes, Rainer Pöttgen, Dirk Johrendt

  06/2008;

  The ternary iron arsenide BaFe2As2 with the tetragonal ThCr2Si2-type structure exhibits a spin density wave (SDW) anomaly at 140 K, very similar to LaFeAsO, the parent compound of the iron arsenide superconductors. BaFe2As2 is a poor Pauli-paramagnetic metal and undergoes a structural and magnetic p... [more] The ternary iron arsenide BaFe2As2 with the tetragonal ThCr2Si2-type structure exhibits a spin density wave (SDW) anomaly at 140 K, very similar to LaFeAsO, the parent compound of the iron arsenide superconductors. BaFe2As2 is a poor Pauli-paramagnetic metal and undergoes a structural and magnetic phase transition at 140 K, accompanied by strong anomalies in the specific heat, electrical resistance and magnetic susceptibility. In the course of this transition, the space group symmetry changes from tetragonal (I4/mmm) to orthorhombic (Fmmm). 57Fe Moessbauer spectroscopy experiments show a single signal at room temperature and full hyperfine field splitting below the phase transition temperature (5.2 T at 77 K). Our results suggest that BaFe2As2 can serve as a new parent compound for oxygen-free iron arsenide superconductors.

• A 57Fe Moessbauer Spectroscopy Study of the 7 K Superconductor LaFePO

  Marcus Tegel, Inga Schellenberg, Rainer Pöttgen, Dirk Johrendt

  06/2008;

  A polycrystalline sample of superconducting LaFePO was prepared in a tin flux at 1123 K. The structure was determined from single crystal data (ZrCuSiAs-type, P4/nmm, a = 3.9610(1), c = 8.5158(2) A, Z = 2) and the phase analysis was performed by the Rietveld method. LaFePO is Pauli-paramagnetic and ... [more] A polycrystalline sample of superconducting LaFePO was prepared in a tin flux at 1123 K. The structure was determined from single crystal data (ZrCuSiAs-type, P4/nmm, a = 3.9610(1), c = 8.5158(2) A, Z = 2) and the phase analysis was performed by the Rietveld method. LaFePO is Pauli-paramagnetic and becomes superconducting at 7 K after removing the ferromagnetic impurity phase Fe2P from the sample. 57Fe Moessbauer spectroscopy measurements at 298, 77, 4.2 and 4 K show single signals at isomer shifts around 0.35 mm/s, subject to weak quadrupole splitting. At 4 K, a symmetric line broadening appears, resulting from a small transferred magnetic hyperfine field of 1.15(1) T and accompanied by an angle of 54.7(5) between Bhf and Vzz, the main component of the electric field gradient tensor.

• Synthesis, Crystal Structure and Magnetism of EuMnPF

  Marcus Tegel, Simon Welzmiller, Dirk Johrendt

  Z. Anorg. Allg. Chem. 01/2008; 634:2085.

• Magnetic, optical, and electronic properties of the phosphide oxides REZnPO (RE = Y, La-Nd, Sm, Gd, Dy, Ho)

  H. Lincke, R. Glaum, V. Dittrich, M. Tegel, D. Johrendt, W. Hermes, M. H. Moller, T. Nilges, R. Pottgen

  Zeitschrift Fur Anorganische Und Allgemeine Chemie. 01/2008; 634:1339-1348.

  Well-shaped yellow to red transparent single crystals of the phosphide oxides REZnPO (RE = Y, La-Nd, Sin, Gd, Dy, Ho) were synthesized from the elements and ZnO in NaCl/KCl fluxes in sealed silica ampoules. Four structures (NdZnPO type, R (3) over barm) were refined from single crystal X-ray diffrac... [more] Well-shaped yellow to red transparent single crystals of the phosphide oxides REZnPO (RE = Y, La-Nd, Sin, Gd, Dy, Ho) were synthesized from the elements and ZnO in NaCl/KCl fluxes in sealed silica ampoules. Four structures (NdZnPO type, R (3) over barm) were refined from single crystal X-ray diffractometer data: a = 388.5(2), c = 3032(1) pm, wR2 = 0.0380, 360 F-2 values for YZnPO, a = 394.6(2), c = 3071(1) pm, wR2 = 0.0587, 226 F-2 values for SmZnPO, a = 392.2(2), c = 3056(1) pm. wR2 = 0.0262, 462 F-2 values for GdZnPO, and a = 389.33(6), c = 3030.5(4) pm, wR2 = 0.0453, 217 F-2 values for DyZnPO each with 14 variables per refinement. The structures are composed of alternate stacks of (RE3+O2-) and (Zn2+P3-) layers with covalent RE-O and Zn-P bonding within and weak ionic bonding between the layers. The zinc and oxygen atoms have slightly distorted tetrahedral coordination by atoms of phosphorus and the rare earth element, respectively. According to the electron precise formulation RE3+Zn2+P3-O2-, these pnictide oxides are transparent in visible light. Susceptibility measurements on beta-CeZnPO, beta-PrZnPO, and GdZnPO reveal Curie-Weiss paramagnetism with experimental magnetic moments of 2.31, 3.60, and 7.72 mu(B)/RE atoms, respectively. beta-CeZnPO and beta-PrZnPO show antiferromagnetic order with Neel temperatures of 7.4 (Ce) arid 2.2 (Pr) K. GdZnPO shows no magnetic ordering down to 2 K. Single crystal absorption spectra measured for REZnPO (RE = Y, La, Pr, Nd, Sm, Dy) in the NIR-Vis region reveal unexpected variations for the optical band gap of these phosphide oxides. For RE = Pr, Nd, Sm, Dy, Ho f-f electronic transitions with nicely resolved ligand-field splittings are observed in the range 6000-20000 cm(-1). DFT band structure calculations show similarity between the valence bands of tetragonal and rhombohedral REZnPO as they possess mainly P-3p character. In both cases. the conduction bands have mainly Zn-4s character, but a significant contribution of RE-5d occurs in rhombohedral REZnPO, which is responsible for a smaller optical band gap for the latter compounds. Variations of the energy gaps of tetragonal REZnPO can be explained by hybridization of Zn-4s + RE-5d + RE-4f orbitals for the conduction band. DFT volume optimizations of alpha- and beta-PrZnPO show beta-PrZnPO to be more stable by 10.7 kJ mol (1).

• Synthesis, crystal structure and superconductivity of LaNiPO

  M. Tegel, D. Bichler, D. Johrendt

  Solid State Sciences. 01/2008; 10:193-197.

  Single crystals of LaNiPO were synthesized by reacting La, P and NiO at 1173 K in a tin flux under argon atmosphere. A phase analysis and crystal structure determination was carried out using X-ray powder and single crystal methods. The quaternary phosphide oxide crystallizes in the tetragonal ZrCuS... [more] Single crystals of LaNiPO were synthesized by reacting La, P and NiO at 1173 K in a tin flux under argon atmosphere. A phase analysis and crystal structure determination was carried out using X-ray powder and single crystal methods. The quaternary phosphide oxide crystallizes in the tetragonal ZrCuSiAs structure (P4/nmm, a = 404.53(1) pm, c = 810.54(3) pm, Z = 2), which is characterized by layers of edge-sharing (2)(infinity) [La4/4O] and (2)(infinity) [NiP4/4] tetrahedra alternating along [001]. LaNiPO is a Pauli paramagnetic metal at room temperature and becomes a type-II superconductor at T-C = 4.3 K with an upper critical field H-c2 approximate to 320 mT at 1.8 K. Connections between the crystal chemistry and the occurrence of superconductivity in LaNiPO and related ThCr2Si2 type compounds are discussed. (C) 2007 Elsevier Masson SAS. All rights reserved.

• Synthesis, crystal structure and spin-density-wave anomaly of the iron arsenide-fluoride SrFeAsF

  M TEGEL, S JOHANSSON, V WEISS, et al.

  EPL. 01/2008; 84.
• 2.90

  Impact points

  Chemical bonds without "chemical bonding"? A combined experimental and theoretical charge density study on an iron trimethylenemethane complex.

  Louis J Farrugia, Cameron Evans, Marcus Tegel

  The journal of physical chemistry. A. 07/2006; 110(25):7952-61.

  High-resolution X-ray diffraction data, in conjunction with DFT(B3LYP) quantum calculations, have been used in a QTAIM analysis of the charge density in the trimethylenemethane (TMM) complex Fe(eta(4)-C[CH(2)](3))(CO)(3). The agreement between the theoretical and experimental topological properties ... [more] High-resolution X-ray diffraction data, in conjunction with DFT(B3LYP) quantum calculations, have been used in a QTAIM analysis of the charge density in the trimethylenemethane (TMM) complex Fe(eta(4)-C[CH(2)](3))(CO)(3). The agreement between the theoretical and experimental topological properties is excellent. Only one bond path is observed between the TMM ligand and the Fe atom, from the central C(alpha) atom. However, much evidence, including from the delocalization indices and the source function, suggests that there is a strong chemical interaction between the Fe and C(beta) atoms, despite the formal lack of chemical bonding according to QTAIM.