Publications in 2023 

(197.) coming soon: Cation diffusion in beta-alumina as seen by 23Na NMR, S. Lunghammer, K. Hogrefe, H. M. R. Wilkening, in preparation, 2023; (198.) Sodium insertion in nanocrystalline LTO, M. Brinek, B. Gadermaier, I. Hanzu and H. M. R. Wilkening, 2023; (199.) Li Ion Hopping in LTPS, D. Prutsch, H. M. R. Wilkening, in preparation, 2023. 

(196.)  Anisotropic Li Diffusion in Li3InCl6, F. Stainer, H. M. R. Wilkening, in preparation (2023).

(195.)  Ion Dynamics in Li4PS4I, A. Jodlbauer, J. Spychala, et al. H. M. R. Wilkening, in preparation (2023).

(194.)  Tuning the ion conductivity of Zr-based metal organic framework ionogels by linker functionalization, A. Ferbezar, R. Zettls, H. Fitzek, B. Gadermaier, H. M. R. Wilkening, I. Hanzu, in preparation (2023).

(193.)  Two mobile ions: proton diffusion in LLZTO garnets, M. Gombotz, C. Hiebl, A. Wilkening, F. Stainer, H. M. R. Wilkening, submitted (2023).

(192.)  The Batteries' New Clothes: Li and H Dynamics in Poorly Conducting Li2OHCl Directly Probed by Nuclear Spin Relaxation, J. Spychala, A. Wilkening and H. M. R. Wilkening, J. Phys. Chem. C link (2023).

(191).  Fast Na+ ion dynamics in the Nb bearing NaSICON Na3+xzNbzZr2−zSi2+xP1−xO12 as probed by Na(23) NMR and conductivity spectroscopy, F. Stainer, B. Gadermaier, A. Kügerl, L. Ladenstein, K. Hogrefe, and H. M. R. Wilkening, Solid State Ionics 395 (2023) 116209.

(190.)  Accounting for Stray Capacitances in Impedance Measuring Cells — A Mandatory Step in the Investigation of Solid Ion Conductors, A. Komar, D. Wilmer, H. Martin R. Wilkening, I. Hanzu, Solid State Ionics 393 (2023) 116196.

(189.)  Energetically preferred Li+ ion jump processes in crystalline solids: Site-specific hopping in β-Li3VF6 as revealed by high-resolution Li(6) 2D EXSY NMR, P. Bottke, K. Hogrefe, J. Kohl, S. Nakhal, A. Wilkening, P. Heitjans, M. Lerch and H. M. R. Wilkening, Mat. Res. Bull. 162 (2023) 112193.

(188.) Understanding Fast Ion Dynamics in Li4NaxTi5O12: From Interfacial to Extended Li and Na Dynamics in its Mixed-Conducting Solid Solutions, P. Posch, S. Lunghammer, A. Wilkening, K. Hogrefe, H. M. R. Wilkening, J. Phys.: Energy 5 (2023) 015001.

Publications in 2022

(187.)  Ionic Transport in Orthorhombic PbF2, T. Scheiber, M. Gombotz, K. Hogrefe, H. M. R. Wilkening, Solid State Ionics 387 (2022) 116077.

(186.) Ionic Transport and Electrochemical Properties of NaSICON-type Li1+xHf2–xGax(PO4)for All-Solid-State Lithium Batteries, L. Ladenstein, K. Hogrefe, H. M. R. Wilkening, ACS Appl. Energy Mater. 5 (2022) 8823.

(185.) Li ion transport in micro- and nanocrystalline Li2S, M. Gombotz, A. Wilkening, H. M. R. Wilkening, Z. Naturf. B, 77 (2022) 397.

(ad 133.) correction to: "Untangling Structure and Dynamics of Lithium-Rich Anti-Perovskites Envisaged as Solid Electrolytes for Batteries" Isabel Hanghofer, G. J. Redhammer, S. Rohde, I. Hanzu, A. Senyshyn, H. M. R. Wilkening, and D. Rettenwander, Chem. Mater. 34 (2022) 5320.

(184.) Ionic Conductivity of Nanocrystalline and Amorphous Li10GeP2S12: The Detrimental Impact of Local Disorder on Ion Transport, L. Schweiger, K. Hogrefe, B. Gadermaier, J. L. M. Rupp, H. M. R. Wilkening, J. Am. Chem. Soc. 144 (2022) 9597.

(183.) Ionic transport in K2Ti6O13, O. Skurikhina, M. Gombotz, M. Senna, M. Fabian, K. L. Da Silva, M. Achimovicov, H. M. R. Wilkening, B. Gadermaier, Z. Phys. Chem. 6-8 (2022) 1077.

(182.) Opening Diffusion Pathways through Site Disorder: The Interplay of Local Structure and Ion Dynamics in the Solid Electrolyte Li6+xP1–xGexS5I as Probed by Neutron Diffraction and NMR, K. Hogrefe, N. Minafra, I. Hanghofer, A. Banik, W. G. Zeier, and H. M. R. Wilkening, J. Am. Chem. Soc. 144 (2022) 1795.

(181.) Extremely Fast Interfacial Li Ion Dynamics in Crystalline LiTFSI Combined with EMIM-TFSI, B. Stanje and H. M. R. Wilkening, ACS Phys. Chem. Au 2 (2022) 136.

(180.) F anion transport in nanocrystalline SmF3 and in mechanosynthesized, vacancy-rich Sm1-xBaxF3-x (Sm0.9Ba0.1F2.9), M. Gombotz, K. Hogrefe, A. Wilkening, B. Gadermaier, and H. M. R. Wilkening, Z. Phys. Chem. 6-8 (2022) 1089

(179.) A lithium-silicon microbattery with anode and housing directly made from semiconductor grade monocrystalline Si, M. Sternad, G. Hirtler, M. Sorger, D. Knez, K. Karlovsky, M. Forster, and H. M. R. Wilkening, Adv. Mater. Technol. 7 (2022) 2100405.

Publications in 2021 (peer rev.)

(178.) With a Little Help from 31P NMR: The Complete Picture on Localized and Long-Range Li+ Diffusion in Li6PS5I, K. Hogrefe, I. Hanghofer, and H. M. R. Wilkening, J. Phys. Chem. C 125 (2021) 22457.

(177.) Fuzzy Logic: About the Origins of Fast Ion Dynamics in Crystalline Solids, M. Gombotz, K. Hogrefe, R. Zettl, B. Gadermaier, and H. M. R. Wilkening, Phil. Trans. R. Soc. A 379 (2021) 20200434 (invited paper).

(176.) Isolable Geminal Bisgermenolates: A New Synthon in Organometallic Chemistry, M. Drusgala, P. Frühwirt, G. Glotz, K. Hogrefe, A.Torvisco, R. C. Fischer, H. M. R. Wilkening, A.-M. Kelterer, G. Georg Gescheidt, M. Haas, Angew. Chem. Int. Ed. 133 (2021) 23838.

(175.) Broadband impedance spectroscopy of Li4Ti5O12: from nearly constant loss to long-range ion dynamics, B. Gadermaier, K. Hogrefe, P. Heitjans, and H. M. R. Wilkening, Z. Allg. Anorg. Chem., 2021, in press (invited paper).

(174.) Insulator:Conductor Interfacial Regions — Li Ion Dynamics in the Nanocrystalline Dispersed Ionic Conductor LiF:TiO2, M. Gombotz, K. P. Pree, V. Pregartner, B. Gadermaier, K. Hogrefe,
I. Hanzu, and H. M. R. Wilkening, Solid State Ionics 369 (2021) 115726.

(173.) Conductor:Insulator Interfaces in Solid Electrolytes: A Design Principle to Enhance Li-Ion Dynamics in Nanoconfined LiBH4:Al2O3, R. Zettl, K. Hogrefe, B. Gadermaier, I. Hanzu, P. Ngene, P. E. de Jongh, and H. M. R. Wilkening, J. Phys. Chem. C 125 (2021) 27 15052-15060.

(172.) Ionic and Electronic Transport in the Fast Ag+ Conductor alpha-Ag3SI, M. Gombotz, I. Hanghofer, S. Eisbacher-Lubensky, and H. M. R. Wilkening, Solid State Sci. 118 (2021) 106680.

(171.) High Li+ and Na+ Conductivity in Hybrid Solid Electrolytes Based on the Porous MIL-121 Metal Organic Framework, R. Zettl, S. Lunghammer, B. Gadermaier, A. Boulaoued, P. Johansson, H. M. R. Wilkening, and I. Hanzu, Adv. Energy. Mater. 16 (2021) 2003542.

(170.) Direct assessment of ultraslow Li jump processes in single crystalline Li3N by 1D 7Li spin-alignment echo NMR, B. Gadermaier, K. Hogrefe, P. Heitjans, and H. M. R. Wilkening, Eur. J. Inorg. Chem. 11 (2021) 1028-1033 (invited paper).

(169.) Tracking Ions the Direct Way: Long-Range Li+ Dynamics in the Thio-LISICON Family Li4MCh4 (M = Sn, Ge; Ch = S, Se) as Probed by 7Li Spin-Alignment Echo NMR, K. Hogrefe, N. Minafra, W. G. Zeier, and H. M. R. Wilkening, J. Phys. Chem. C 125, 4 (2021) 2306–2317 (invited paper).

(168.) Two-dimensional substitution: towards a better understanding of the structure-transport correlations in the Li-superionic thio-LISICONs, N. Minafra, K. Hogrefe, F. Barbon, B. Helm, C. Li, H. M. R. Wilkening, W. G. Zeier, Chem. Mater. 33, 2 (2021) 727–740.

(167.) Fast Li ion dynamics in the mechanosynthesized nanostructured form of the solid electrolyte Li3YBr6, M. Gombotz and H. M. R. Wilkening, ACS Sust. Chem. Eng. 9, 2 (2021) 743–755 (invited paper).

Publications in 2020 (peer rev.)

(166.)  A New Solar-Cell-Battery Hybrid Energy System: Integrating Organic Photovoltaics with Li-Ion and Na-Ion Technologies, S. F. Hoefler, R. Zettl, D. Knez, G. Haberfehlner, F. Hofer, T. Rath, G. Trimmel, H. M. R. Wilkening and I. Hanzu, ACS Sust. Chem. Eng. 8 (2020) 19155.

(165.) Lowering the interfacial resistance in LLZTO|poly(ethylene oxide) composite electrolytes, E. Kuhnert, L. Ladenstein, A. Jodlbauer, C. Slugovc, G. Trimmel, H. M. R. Wilkening, D. Rettenwander, Cell Press Phys. Sci. 1 (2020) 100214.

(164.) Safety assessment of electrically cycled cells at high temperatures under mechanical crush loads, G. Kovachev, C. Ellersdorfer, G. Gstrein, H. Hanzu, H. M. R. Wilkening, T. Werling, F. Schauwecker, W. Sinz, eTransportation 6 (2020) 100087.

(163.)  Highly Conductive Garnet-Type Electrolytes: Access to Li6.5La3Zr1.5Ta0.5O12 Prepared by Molten Salt and Solid-State Methods, P. Badami, J. M. Weller, A. Wahab, G.J. Redhammer, L. Ladenstein, D. Rettenwander, M. Wilkening, C. K. Chan and A. M. Kannan, ACS Appl. Mater. Interf. 12 (2020) 48580.

(162.)  Structural Disorder in Li6PS5I Speeds 7Li Nuclear Spin Recovery and Slows Down 31P Relaxation — Implications for Translational and Rotational Jumps as Seen by NMR, M. Brinek, C. Hiebl, K. Hogrefe, I. Hanghofer, and H. M. R. Wilkening, J. Phys. Chem. C 124 (2020) 22934.

(161.)  Rapid Low-Dimensional Li+ Ion Hopping Processes in Synthetic Hectorite-Type Li0.5[Mg2.5Li0.5]Si4O10F2, C. Hiebl, P. Loch, M. Brinek, M. Gombotz, B. Gadermaier, P. Heitjans, J. Breu, and H. M. R. Wilkening, Chem. Mater. 32 (2020) 7445.

(160.)  Li-Ion Diffusion in Anion-Substituted Nanoconfined Hydrides: LiBH4-LiI:Al2O3: From 2D Bulk Transport to Interfacial Dynamics, R. Zettl, M. Gombotz, D. Clarkson, S. Greenbaum, P. Ngene, P. E. de Jongh, and H. M. R. Wilkening, ACS Appl. Mater. Interfaces 12 (2020) 38570.

(159.)  Anomalies in Bulk Ion Transport in the Solid Solutions of Li7La3M2O12 (M = Hf, Sn) and Li5La3Ta2O12, L. Ladenstein, S. Simic, G. Kothleitner, D. Rettenwander, H. M. R. Wilkening, J. Phys. Chem. C 124 (2020) 16796.

(158.)  The Electronic Conductivity of Single Crystalline Ga-Stabilized Cubic Li7La3Zr2O12 — A Technologically Relevant Parameter for All-Solid-State Batteries, M. Philipp, B. Gadermaier, P. Posch, I. Hanzu, S. Ganschow, M. Meven, D. Rettenwander, G. J. Redhammer, and H. M. R. Wilkening, Adv. Mater. Interf. 7 (2020) 2000450.

(157.)  Influence of defects on ionic transport in LiTaO3 - a study using EXAFS and positron annihilation lifetime spectroscopy, B. Gadermaier, L. Resch, D. Pickup, I. Hanghofer, I. Hanzu, P. Heitjans, W. Sprengel, R. Würschum, A. Chadwick, H. M. R. Wilkening, Solid State Ionics 32 (2020) 115355.

(156.)  Understanding the Origin of Enhanced Li-Ion Transport in Nanocrystalline Argyrodite-Type Li6PS5I, M. Brinek, C. Hiebl, H. M. R. Wilkening, Chem. Mater. 32 (2020) 4754.

(155.)  The natural critical current density limit for Li7La3Zr2O12 garnets, F. Flatscher, S. Ganschow, H. M. R. Wilkening, D. Rettenwander, J. Mater. Chem. A 8 (2020) 15782.

(154.)  On the dependence of ionic transport on crystal orientation in NaSICON-type solid electrolytes, L. Ladenstein, S. Lunghammer, E. Wang, L. Miara, M. Wilkening, G. Redhammer, D. Rettenwander, J. Phys.: Energy 2 (2020) 035003.

(153.)  Lithium-Ion Transport in Nanocrystalline Spinel-type Li[InxLiy]Br4 as Seen by Conductivity Spectroscopy and NMR, M. Gombotz, D. Rettenwander, H. M. R. Wilkening, Front. Chem. 8 (2020) 100.

(152.)  Combined Effects of Anion Substitution and Nanoconfinement on the Ionic Conductivity of Li-Based Complex Hydrides, R. Zettl, L. de Kort, M. Gombotz, H. M. R. Wilkening, P. de Jongh, P. Ngene, J. Phys. Chem. 124 C (2020) 2806.

(151.)  Ion Dynamics in Al-Stabilized Li7La3Zr2O12 Single Crystals – Macroscopic Transport and the Elementary Steps of Ion Hopping, P. Posch, S. Lunghammer, S. Berendts, S. Ganschow, G. J. Redhammer, A. Wilkening, M. Lerch, B. Gadermaier, D. Rettenwander, H. M. R. Wilkening, Energy Storage Mater. 24 (2020) 220.

Publications in 2019 (peer rev.) 

(150.)  Self-diffusion and ionic exchange in mechanosynthesized, nanocrystalline solid solutions of PbF2 and CaF2  – 19F 2D NMR visualizes the flourine hopping preferences, S. Lunghammer, P. Posch, A. Düvel, B. Kunert, R. Resel and H. M. R. Wilkening, Solid State Ionics 343 (2019) 115067.

(149.)  Analytical dissection of an automotive Li-ion pouch cell, G. Kovachev, H. Schröttner, G. Gstrein, L. Aiello, W. Sinz, C. Ellersdorfer, I. Hanzu, H. Martin R. Wilkening, A. Foitzik, M. Wellm, Batteries 5 (2019) 67.

(148.)  Fluoride-Ion Batteries: On the Electrochemical Stability of Nanocrystalline La0.9Ba0.1F2.9 Against Metal Electrodes, M. Gombotz, V. Pregartner, I. Hanzu, H. M. R. Wilkening, Nanomaterials 9 (2019) 1517.

(147.) Evaluation of carboxylic, phosphonic and sulfonic acid protogenic moieties on tunable poly(meta-phenylene oxide) ionomer scaffolds, R. Hudson, R. Adhikari, M. Wilkening, S. Thayumanavan, M. Tuominen, I. Hanzu, J. Katz, J. Polym. Sci. Part A: Polym. Chem. 57 (2019) 2209.

(146.)  Redox processes in sodium vanadium phosphate cathodes – insights from operando magnetometry, G. Klinser, R. Zettl, M. Wilkening, H. Krenn,  I. Hanzu, R. Würschum, Phys. Chem. Chem. Phys. 21 (2019) 20151

(145.)  Superionic Diffusion through Frustrated Energy Landscape, D. Di Stefano, A. Miglio, K. Robeyns, Y. Filinchuk, M. Lechartier, A. Senyshyn, H. Ishida, S. Spannenberger, D. Prutsch, S. Lunghammer, D. Rettenwander, M. Wilkening, B. Roling, Y. Kato, G. Hautier, Chem 5 (2019) 2450.

(144.)  Lithium Ion Dynamics in LiZr2(PO4)3 and Li1.4Ca0.2Zr1.8(PO4)3, I. Hanghofer, B. Gadermaier, A. Wilkening, D. Rettenwander and H. M. R. Wilkening, Dalton Trans. 48 (2019) 9376.

(143.) Fast Rotational Dynamics in Argyrodite-Type Li6PS5X (X: Cl, Br, I) as Seen by 31P Nuclear Magnetic Relaxation On Cation−Anion Coupled Transport in Thiophosphates, I. Hanghofer, B. Gadermaier, and H. M. R. Wilkening, Chem. Mater. 31 (2019) 4591.

(142.)  Ionic Conduction Mechanism in the Na2(B12H12)0.5(B10H10)0.5 closo-Borate Solid-State Electrolyte: Interplay of Disorder and Ion-Ion Interactions, L. Duchêne, S. Lunghammer, T. Burankova, W.-C. Liao, J. P. Embs, C. Copéret, H. M. R. Wilkening, A. Remhof, H. Hagemann, C. Battaglia, Chem. Mater. 31 (2019) 3449.

(141.)  Substitutional disorder: structure and ion dynamics of the argyrodites Li6PS5Cl, Li6PS5Br and Li6PS5I,  I. Hanghofer, M. Brinek, S. L. Eisbacher, B. Bitschnau, M. Volck, V. Hennige, I. Hanzu, D. Rettenwander, H. M. R. Wilkening, Phys. Chem. Chem. Phys. 21 (2019) 8489.

(140.)  Glass in Two Forms: Heterogeneous Electrical Relaxation in Nanoglassy Petalite, B. Gadermaier, B. Stanje, A. Wilkening, I. Hanzu, P. Heitjans, H. M. R. Wilkening, J. Phys. Chem. C 123 (2019) 10153.

(139.)  Dispersed Solid Conductors: Fast Interfacial Li Ion Dynamics in Nanostructured LiF and LiF:Al2O3 Composites, S. Breuer, V. Pregartner, S. Lunghammer, H. M. R. Wilkening, J. Phys. Chem. C 123 (2019) 5222.

(138.)  Electrochemical Properties of Arylsilanes − A Mechanistic and Kinetics Investigation, J. Biedermann, H. M. R. Wilkening, F. Uhlig, I. Hanzu, Electrochem. Commun. 102 (2019) 13.

(137.)  Spatial confinement − Rapid 2D F diffusion in microcrystalline and nanocrystalline RbSn2F5, M. Gombotz, S. Lunghammer, S. Breuer, I. Hanzu, F. Preishuber-Pflügl and H. Martin R. Wilkening, Phys. Chem. Chem. Phys. 21 (2019) 1872.

(136.)   Nascent SEI-Surface Films on Single Crystalline Silicon Investigated by Scanning Electrochemical Microscopy, E. dos Santos Sardinha, M. Sternad, H. Martin R. Wilkening, G. Wittstock, ACS Appl. Energy Mater. 2 (2019) 1388.

(135.)  Rapid Hydrogen Bulk Diffusion in Cubic LLZO Garnets as Probed by Single X-Ray Diffraction, C. Hiebl, D. Young, R. Wagner, H. M. R. Wilkening, G. Redhammer, D. Rettenwander, J. Phys. Chem. C 123 (2019) 1094.

(134.)  Heterogeneous F anion transport, local dynamics and electrochemical stability of nanocrystalline La1−xBaxF3−x, S. Breuer, M. Gombotz, V. Pregartner, I. Hanzu, H. M. R. Wilkening, Energy Storage Mater. 16 (2019) 481.

Publications in 2018 (peer rev.)

(133.)  Untangling Structure and Dynamics of Lithium-Rich Anti-Perovskites Envisaged as Solid Electrolytes for Batteries, Isabel Hanghofer, G. J. Redhammer, S. Rohde, I. Hanzu, A. Senyshyn, H. M. R. Wilkening, and D. Rettenwander, Chem. Mater 30 (2018) 8134.

(132.)  Nuclear spin relaxation in nanocrystalline β-Li3PS4 reveals low-dimensional Li diffusion in an isotropic matrix, D. Prutsch, B. Gadermaier, H. Brandstätter, V. Pregartner, B. Stanje, D. Wohlmuth, V. Epp, D. Rettenwander, I. Hanzu, and H. M. R. Wilkening, Chem. Mater 30 (2018) 7575.

(131.)  Mismatch in cation size causes rapid anion dynamics in solid electrolytes: the role of the Arrhenius prefactor, S. Breuer, M. Wilkening, Dalton Trans. 47 (2018) 4105.

(130.)  Bulk and g.b. ionic conductivity in sodium zirconophosphosilicate Na3
Zr2(SiO4)2PO4 (NASICON), S. Lunghammer, Q. Ma, D. Rettenwander, F. Tietz, M. Wilkening, Chem. Phys. Lett. 701 (2018) 147.

(129.)  F anion dynamics in cation-mixed nanocrystalline LaF3:SrF2, S. Breuer, S. Lunghammer, A. Kiesl, M. Wilkening, J. Mater. Sci. 53 (2018) 13669. 

(128.)  Long Chain Li and Na Alkyl Carbonates as Solid Electrolyte Interface Components: Structure, Ion Transport and Mechanical Properties, L. Schafzahl, H. M. A. Ehmann, M. Kriechbaum, J. Sattelkow, T. Ganner, H. Plank, M. Wilkening, S. A. Freunberger, Chem. Mater. 30 (2018) 3338.

(127.)  Fluorine Translational Anion Dynamics in Nanocrystalline Ceramics: SrF2-YF3 Solid Solutions, S. Breuer, B. Stanje, V. Pregartner, S. Lunghammer, I. Hanzu, M. Wilkening, Crystals 8 (2018) 122.

(126.)  Ion Dynamics in a New Class of Materials: Nanoglassy Lithium Alumosilicates, B. Stanje, P. Bottke, S. Breuer, I. Hanzu, P. Heitjans, M. Wilkening, Mat. Res. Express 5 (2018) 035202.

(125.)  Rapid Li ion dynamics in the interfacial regions of nanocrystalline solids, S. Breuer, M. Uitz, M. Wilkening, J. Phys. Chem. Lett. 9 (2018) 2093.

(124.)  Arrhenius behaviour of the bulk Na-ion conductivity in Na3Sc2(PO4)3 single crystals observed by microcontact impedance spectroscopy, D. Rettenwander, G. J. Redhammer, M. Guin, A. Benisek, H. Krüger, M. Wilkening, F. Tietz J. Fleig, Chem. Mater. 30 (2018) 1776.

(123.)  Interface instability of Fe-stabilized Li7La3Zr2O12 versus Li metal, D. Rettenwander, R. Wagner, A. Reyer, M. Bonta, L. Cheng, M. M. Doeff, A. Limbeck, M. Wilkening, G. Amthauer, J. Phys. Chem. C 122 (2018) 3780.

(122.)  Fast Na ion transport triggered by rapid ion exchange on local length scales: 23Na NMR spin-lattice relaxation reveals ultrafast Na ion dynamics in the solid electrolyte Na3.4Sc0.4Zr1.6(SiO4)2PO4, S. Lunghammer, D. Prutsch, S. Breuer, D. Rettenwander, I. Hanzu, Q. Ma, F. Tietz, M. Wilkening, Sci. Rep. 8 (2018) 11970.

(121.)  Quantifying Total Superoxide, Peroxide and Carbonaceous Compounds in Metal-O2 Batteries and the Solid Electrolyte Interphase, B. Schafzahl, E. Mourad, L. Schafzahl, Y. Petit, A. Raju, M. Thotiyl, M. Wilkening, C. Slugovc, S. Freunberger, ACS Energy Lett. 3 (2018) 170. 

(c) Lunghammer - TU Graz