TY - JOUR
AB - A series of new organic donor–π–acceptor dyes incorporating a diquat moiety as a novel electron-acceptor unit have been synthesized and characterized. The analytical data were supported by DFT calculations. These dyes were explored in the aerobic thiocyanation of indoles and pyrroles. Here they showed a high photocatalytic activity under visible light, giving isolated yields of up to 97 %. In addition, the photocatalytic activity of standalone diquat and methyl viologen through formation of an electron donor acceptor complex is presented.
AU - Meier, Armin
AU - Badalov, Sabuhi
AU - Biktagirov, Timur
AU - Schmidt, Wolf Gero
AU - Wilhelm, René
ID - 43827
IS - 22
JF - Chemistry – A European Journal
KW - General Chemistry
KW - Catalysis
KW - Organic Chemistry
SN - 0947-6539
TI - Diquat Based Dyes: A New Class of Photoredox Catalysts and Their Use in Aerobic Thiocyanation
VL - 29
ER -
TY - JOUR
AU - Ruiz Alvarado, Isaac Azahel
AU - Zare Pour, Mohammad Amin
AU - Hannappel, Thomas
AU - Schmidt, Wolf Gero
ID - 49634
IS - 4
JF - Physical Review B
SN - 2469-9950
TI - Structural fingerprints in the reflectance anisotropy of AlInP(001)
VL - 108
ER -
TY - CHAP
AB - Lithium niobate (LiNbO3), a material frequently used in optical applications, hosts different kinds of polarons that significantly affect many of its physical properties. In this study, a variety of electron polarons, namely free, bound, and bipolarons, are analyzed using first-principles calculations. We perform a full structural optimization based on density-functional theory for selected intrinsic defects with special attention to the role of symmetry-breaking distortions that lower the total energy. The cations hosting the various polarons relax to a different degree, with a larger relaxation corresponding to a larger gap between the defect level and the conduction-band edge. The projected density of states reveals that the polaron states are formerly empty Nb 4d states lowered into the band gap. Optical absorption spectra are derived within the independent-particle approximation, corrected by the GW approximation that yields a wider band gap and by including excitonic effects within the Bethe-Salpeter equation. Comparing the calculated spectra with the density of states, we find that the defect peak observed in the optical absorption stems from transitions between the defect level and a continuum of empty Nb 4d states. Signatures of polarons are further analyzed in the reflectivity and other experimentally measurable optical coefficients.
AU - Schmidt, Falko
AU - Kozub, Agnieszka L.
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
AU - Schindlmayr, Arno
ED - Corradi, Gábor
ED - Kovács, László
ID - 30288
SN - 978-3-0365-3340-7
T2 - New Trends in Lithium Niobate: From Bulk to Nanocrystals
TI - Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response
ER -
TY - JOUR
AB - AbstractPolarons influence decisively the performance of lithium niobate for optical applications. In this work, the formation of (defect) bound polarons in lithium niobate is studied by ab initio molecular dynamics. The calculations show a broad scatter of polaron formation times. Rising temperature increases the share of trajectories with long formation times, which leads to an overall increase of the average formation time with temperature. However, even at elevated temperatures, the average formation time does not exceed the value of 100 femtoseconds, i.e., a value close to the time measured for free, i.e., self-trapped polarons. Analyzing individual trajectories, it is found that the time required for the structural relaxation of the polarons depends sensitively on the excitation of the lithium niobate high-frequency phonon modes and their phase relation.
AU - Krenz, Marvin
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
ID - 37711
JF - Applied Physics A
KW - General Materials Science
KW - General Chemistry
SN - 0947-8396
TI - Bound polaron formation in lithium niobate from ab initio molecular dynamics
VL - 128
ER -
TY - JOUR
AB - We study the DC conductivity in potassium titanyl phosphate (KTiOPO4, KTP) and its isomorphs KTiOAsO4 (KTA) and Rb1%K99%TiOPO4 (RKTP) and introduce a method by which to reduce the overall ionic conductivity in KTP by a potassium nitrate treatment. Furthermore, we create so-called gray tracking in KTP and investigate the ionic conductivity in theses areas. A local unintended reduction of the ionic conductivity is observed in the gray-tracked regions, which also induce additional optical absorption in the material. We show that a thermal treatment in an oxygen-rich atmosphere removes the gray tracking and brings the ionic conductivity as well as the optical transmission back to the original level. These studies can help to choose the best material and treatment for specific applications.
AU - Padberg, Laura
AU - Quiring, Viktor
AU - Bocchini, Adriana
AU - Santandrea, Matteo
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
AU - Silberhorn, Christine
AU - Eigner, Christof
ID - 33484
JF - Crystals
SN - 2073-4352
TI - DC Ionic Conductivity in KTP and Its Isomorphs: Properties, Methods for Suppression, and Its Connection to Gray Tracking
VL - 12
ER -
TY - JOUR
AB - Many-body perturbation theory based on density-functional theory calculations is used to determine the quasiparticle band structures and the dielectric functions of the isomorphic ferroelectrics rubidium titanyl phosphate (RbTiOPO4) and potassium titanyl arsenide (KTiOAsO4). Self-energy corrections of more than 2 eV are found to widen the transport band gaps of both materials considerably to 5.3 and 5.2 eV, respectively. At the same time, both materials are characterized by strong exciton binding energies of 1.4 and 1.5 eV, respectively. The solution of the Bethe-Salpeter equation based on the quasiparticle energies results in onsets of the optical absorption within the range of the measured data.
AU - Neufeld, Sergej
AU - Schindlmayr, Arno
AU - Schmidt, Wolf Gero
ID - 26627
IS - 1
JF - Journal of Physics: Materials
TI - Quasiparticle energies and optical response of RbTiOPO4 and KTiOAsO4
VL - 5
ER -
TY - JOUR
AU - Glahn, Luis Joel
AU - Ruiz Alvarado, Isaac Azahel
AU - Neufeld, Sergej
AU - Zare Pour, Mohammad Amin
AU - Paszuk, Agnieszka
AU - Ostheimer, David
AU - Shekarabi, Sahar
AU - Romanyuk, Oleksandr
AU - Moritz, Dominik Christian
AU - Hofmann, Jan Philipp
AU - Jaegermann, Wolfram
AU - Hannappel, Thomas
AU - Schmidt, Wolf Gero
ID - 37656
IS - 11
JF - physica status solidi (b)
KW - Condensed Matter Physics
KW - Electronic
KW - Optical and Magnetic Materials
SN - 0370-1972
TI - Clean and Hydrogen‐Adsorbed AlInP(001) Surfaces: Structures and Electronic Properties
VL - 259
ER -
TY - JOUR
AU - Ruiz Alvarado, Isaac Azahel
AU - Schmidt, Wolf Gero
ID - 37710
IS - 23
JF - ACS Omega
KW - General Chemical Engineering
KW - General Chemistry
SN - 2470-1343
TI - Water/InP(001) from Density Functional Theory
VL - 7
ER -
TY - JOUR
AU - Moritz, Dominik Christian
AU - Ruiz Alvarado, Isaac Azahel
AU - Zare Pour, Mohammad Amin
AU - Paszuk, Agnieszka
AU - Frieß, Tilo
AU - Runge, Erich
AU - Hofmann, Jan P.
AU - Hannappel, Thomas
AU - Schmidt, Wolf Gero
AU - Jaegermann, Wolfram
ID - 37681
IS - 41
JF - ACS Applied Materials & Interfaces
KW - General Materials Science
SN - 1944-8244
TI - P-Terminated InP (001) Surfaces: Surface Band Bending and Reactivity to Water
VL - 14
ER -
TY - JOUR
AU - Karmo, Marsel
AU - Ruiz Alvarado, Isaac Azahel
AU - Schmidt, Wolf Gero
AU - Runge, Erich
ID - 37714
IS - 6
JF - ACS Omega
KW - General Chemical Engineering
KW - General Chemistry
SN - 2470-1343
TI - Reconstructions of the As-Terminated GaAs(001) Surface Exposed to Atomic Hydrogen
VL - 7
ER -
TY - JOUR
AU - Murzakhanov, Fadis F.
AU - Mamin, Georgy Vladimirovich
AU - Orlinskii, Sergei Borisovich
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
AU - Biktagirov, Timur
AU - Aharonovich, Igor
AU - Gottscholl, Andreas
AU - Sperlich, Andreas
AU - Dyakonov, Vladimir
AU - Soltamov, Victor A.
ID - 37713
IS - 7
JF - Nano Letters
KW - Mechanical Engineering
KW - Condensed Matter Physics
KW - General Materials Science
KW - General Chemistry
KW - Bioengineering
SN - 1530-6984
TI - Electron–Nuclear Coherent Coupling and Nuclear Spin Readout through Optically Polarized VB– Spin States in hBN
VL - 22
ER -
TY - JOUR
AU - Bocchini, Adriana
AU - Gerstmann, Uwe
AU - Bartley, Tim
AU - Steinrück, Hans-Georg
AU - Henkel, Gerald
AU - Schmidt, Wolf Gero
ID - 33965
JF - Phys. Rev. Materials
TI - Electrochemical performance of KTiOAsO_4 (KTA) in potassium-ion batteries from density-functional theory
VL - 6
ER -
TY - JOUR
AU - Bocchini, Adriana
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
ID - 31254
JF - Phys. Rev. B
TI - Oxygen vacancies in KTiOPO_4: Optical absorption from hybrid DFT
VL - 105
ER -
TY - JOUR
AB - Hole polarons and defect-bound exciton polarons in lithium niobate are investigated by means of density-functional theory, where the localization of the holes is achieved by applying the +U approach to the oxygen 2p orbitals. We find three principal configurations of hole polarons: (i) self-trapped holes localized at displaced regular oxygen atoms and (ii) two other configurations bound to a lithium vacancy either at a threefold coordinated oxygen atom above or at a two-fold coordinated oxygen atom below the defect. The latter is the most stable and is in excellent quantitative agreement with measured g factors from electron paramagnetic resonance. Due to the absence of mid-gap states, none of these hole polarons can explain the broad optical absorption centered between 2.5 and 2.8 eV that is observed in transient absorption spectroscopy, but such states appear if a free electron polaron is trapped at the same lithium vacancy as the bound hole polaron, resulting in an exciton polaron. The dielectric function calculated by solving the Bethe–Salpeter equation indeed yields an optical peak at 2.6 eV in agreement with the two-photon experiments. The coexistence of hole and exciton polarons, which are simultaneously created in optical excitations, thus satisfactorily explains the reported experimental data.
AU - Schmidt, Falko
AU - Kozub, Agnieszka L.
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
AU - Schindlmayr, Arno
ID - 44088
IS - 11
JF - Crystals
TI - A density-functional theory study of hole and defect-bound exciton polarons in lithium niobate
VL - 12
ER -
TY - JOUR
AU - Jurgen von Bardeleben, Hans
AU - Cantin, Jean-Louis
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
AU - Biktagirov, Timur
ID - 29747
IS - 19
JF - Nano Letters
KW - Mechanical Engineering
KW - Condensed Matter Physics
KW - General Materials Science
KW - General Chemistry
KW - Bioengineering
SN - 1530-6984
TI - Spin Polarization, Electron–Phonon Coupling, and Zero-Phonon Line of the NV Center in 3C-SiC
VL - 21
ER -
TY - JOUR
AU - Slawig, Diana
AU - Gruschwitz, Markus
AU - Gerstmann, Uwe
AU - Rauls, Eva
AU - Tegenkamp, Christoph
ID - 29748
IS - 36
JF - The Journal of Physical Chemistry C
KW - Surfaces
KW - Coatings and Films
KW - Physical and Theoretical Chemistry
KW - General Energy
KW - Electronic
KW - Optical and Magnetic Materials
SN - 1932-7447
TI - Adsorption and Reaction of PbPc on Hydrogenated Epitaxial Graphene
VL - 125
ER -
TY - JOUR
AU - Jain, Mitisha
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
AU - Aldahhak, Hazem
ID - 40250
IS - 6
JF - Journal of Computational Chemistry
KW - Computational Mathematics
KW - General Chemistry
SN - 0192-8651
TI - Adatom mediated adsorption of N‐heterocyclic carbenes on Cu(111) and Au(111)
VL - 43
ER -
TY - JOUR
AB - Lithium niobate (LiNbO3), a material frequently used in optical applications, hosts different kinds of polarons that significantly affect many of its physical properties. In this study, a variety of electron polarons, namely free, bound, and bipolarons, are analyzed using first-principles calculations. We perform a full structural optimization based on density-functional theory for selected intrinsic defects with special attention to the role of symmetry-breaking distortions that lower the total energy. The cations hosting the various polarons relax to a different degree, with a larger relaxation corresponding to a larger gap between the defect level and the conduction-band edge. The projected density of states reveals that the polaron states are formerly empty Nb 4d states lowered into the band gap. Optical absorption spectra are derived within the independent-particle approximation, corrected by the GW approximation that yields a wider band gap and by including excitonic effects within the Bethe-Salpeter equation. Comparing the calculated spectra with the density of states, we find that the defect peak observed in the optical absorption stems from transitions between the defect level and a continuum of empty Nb 4d states. Signatures of polarons are further analyzed in the reflectivity and other experimentally measurable optical coefficients.
AU - Schmidt, Falko
AU - Kozub, Agnieszka L.
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
AU - Schindlmayr, Arno
ID - 21946
JF - Crystals
TI - Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response
VL - 11
ER -
TY - JOUR
AU - Murzakhanov, F. F.
AU - Yavkin, B. V.
AU - Mamin, G. V.
AU - Orlinskii, S. B.
AU - von Bardeleben, H. J.
AU - Biktagirov, Timur
AU - Gerstmann, Uwe
AU - Soltamov, V. A.
ID - 29749
JF - Physical Review B
SN - 2469-9950
TI - Hyperfine and nuclear quadrupole splitting of the NV− ground state in 4H-SiC
VL - 103
ER -
TY - JOUR
AU - Aldahhak, Hazem
AU - Hogan, Conor
AU - Lindner, Susi
AU - Appelfeller, Stephan
AU - Eisele, Holger
AU - Schmidt, Wolf Gero
AU - Dähne, Mario
AU - Gerstmann, Uwe
AU - Franz, Martin
ID - 22010
JF - Physical Review B
SN - 2469-9950
TI - Electronic structure of the Si(111)3×3R30∘−B surface from theory and photoemission spectroscopy
VL - 103
ER -