@article{UtechtPanKlamrothetal.2014, author = {Utecht, Manuel Martin and Pan, Tianluo and Klamroth, Tillmann and Palmer, Richard E.}, title = {Quantum chemical cluster models for chemi- and physisorption of chlorobenzene on Si(111)-7x7}, series = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, volume = {118}, journal = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory}, number = {33}, publisher = {American Chemical Society}, address = {Washington}, issn = {1089-5639}, doi = {10.1021/jp504208d}, pages = {6699 -- 6704}, year = {2014}, abstract = {Motivated by recent atomic manipulation experiments, we report quantum chemical calculations for chemi- and physisorption minima of chlorobenzene on the Si(111)-7x7 surface. A density functional theory cluster approach is applied, using the B3LYP hybrid functional alongside Grimme's empirical dispersion corrections (D3). We were able to identify chemisorption sites of binding energies of 1.6 eV and physisorption energies of 0.6 eV, both in encouraging agreement with the trend of experimental data. The cluster approach opens up the possibility of a first-principles based dynamical description of STM manipulation experiments on this system, the interpretation of which involves both the chemi- and physisorbed states. However, we found that special care has to be taken regarding the choice of clusters, basis sets, and the evaluation of the dispersion corrections.}, language = {en} } @article{UtechtPalmerKlamroth2017, author = {Utecht, Manuel Martin and Palmer, Richard E. and Klamroth, Tillmann}, title = {Quantum chemical approach to atomic manipulation of chlorobenzene on the Si(111)-7 x 7 surface}, series = {Physical review materials}, volume = {1}, journal = {Physical review materials}, number = {2}, publisher = {American Physical Society}, address = {College Park}, issn = {2475-9953}, doi = {10.1103/PhysRevMaterials.1.026001}, pages = {5}, year = {2017}, abstract = {We present a cluster model to describe the localization of hot charge carriers on the Si(111)-7 x 7 surface, which leads to (nonlocal) desorption of chlorobenzene molecules in scanning tunneling microscope (STM) manipulation experiments. The localized charge carriers are modeled by a small cluster. By means of quantum chemical calculations, this cluster model explains many experimental findings from STM manipulation. We show that the negative charge is mainly localized in the surface, while the positive one also resides on the molecule. Both resonances boost desorption: In the negative resonance the adatom is elevated; in the positive one the chemisorption bond between the silicon surface adatom and chlorobenzene is broken. We find normal modes promoting desorption matching experimental low-temperature activation energies for electron-and hole-induced desorption.}, language = {en} } @article{UtechtKlamrothSaalfrank2011, author = {Utecht, Manuel Martin and Klamroth, Tillmann and Saalfrank, Peter}, title = {Optical absorption and excitonic coupling in azobenzenes forming self-assembled monolayers a study based on density functional theory}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {13}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {48}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c1cp22793a}, pages = {21608 -- 21614}, year = {2011}, abstract = {Based on the analysis of optical absorption spectra, it has recently been speculated that the excitonic coupling between individual azobenzene-functionalized alkanethiols arranged in a self-assembled monolayer (SAM) on a gold surface could be strong enough to hinder collective trans-cis isomerization-on top of steric hindrance [Gahl et al., J. Am. Chem. Soc., 2010, 132, 1831]. Using models of SAMs of increasing complexity (dimer, linear N-mers, and two-dimensionally arranged N-mers) and density functional theory on the (TD-) B3LYP/6-31G* level, we determine optical absorption spectra, the nature and magnitude of excitonic couplings, and the corresponding spectral shifts. It is found that at inter-monomer distances of about 20 angstrom and above, TD-B3LYP excitation frequencies (and signal intensities) can be well described by the frequently used point-dipole approximation. Further, calculated blue shifts in optical absorption spectra account for the experimental observations made for azobenzene/gold SAMs, and hint to the fact that they can indeed be responsible for reduced switching probability in densely packed self-assembled structures.}, language = {en} } @article{UtechtKlamroth2018, author = {Utecht, Manuel Martin and Klamroth, Tillmann}, title = {Local resonances in STM manipulation of chlorobenzene on Si(111)-7x7}, series = {Molecular physics}, volume = {116}, journal = {Molecular physics}, number = {13}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {0026-8976}, doi = {10.1080/00268976.2018.1442939}, pages = {1687 -- 1696}, year = {2018}, abstract = {Hot localised charge carriers on the Si(111)-7x7 surface are modelled by small charged clusters. Such resonances induce non-local desorption, i.e. more than 10 nm away from the injection site, of chlorobenzene in scanning tunnelling microscope experiments. We used such a cluster model to characterise resonance localisation and vibrational activation for positive and negative resonances recently. In this work, we investigate to which extent the model depends on details of the used cluster or quantum chemistry methods and try to identify the smallest possible cluster suitable for a description of the neutral surface and the ion resonances. Furthermore, a detailed analysis for different chemisorption orientations is performed. While some properties, as estimates of the resonance energy or absolute values for atomic changes, show such a dependency, the main findings are very robust with respect to changes in the model and/or the chemisorption geometry. [GRAPHICS] .}, language = {en} } @misc{UtechtKlamroth2018, author = {Utecht, Manuel Martin and Klamroth, Tillmann}, title = {Local resonances in STM manipulation of chlorobenzene on Si(111)-7×7}, series = {Molecular Physics}, journal = {Molecular Physics}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-412970}, pages = {11}, year = {2018}, abstract = {Hot localised charge carriers on the Si(111)-7×7 surface are modelled by small charged clusters. Such resonances induce non-local desorption, i.e. more than 10 nm away from the injection site, of chlorobenzene in scanning tunnelling microscope experiments. We used such a cluster model to characterise resonance localisation and vibrational activation for positive and negative resonances recently. In this work, we investigate to which extent the model depends on details of the used cluster or quantum chemistry methods and try to identify the smallest possible cluster suitable for a description of the neutral surface and the ion resonances. Furthermore, a detailed analysis for different chemisorption orientations is performed. While some properties, as estimates of the resonance energy or absolute values for atomic changes, show such a dependency, the main findings are very robust with respect to changes in the model and/or the chemisorption geometry.}, language = {en} } @article{UtechtGaebelKlamroth2018, author = {Utecht, Manuel Martin and Gaebel, Tina and Klamroth, Tillmann}, title = {Desorption induced by low energy charge carriers on Si(111)-7 x 7}, series = {Journal of computational chemistry : organic, inorganic, physical, biological}, volume = {39}, journal = {Journal of computational chemistry : organic, inorganic, physical, biological}, number = {30}, publisher = {Wiley}, address = {Hoboken}, issn = {0192-8651}, doi = {10.1002/jcc.25607}, pages = {2517 -- 2525}, year = {2018}, abstract = {We use clusters for the modeling of local ion resonances caused by low energy charge carriers in STM-induced desorption of benzene derivates from Si(111)-7 x 7. We perform Born-Oppenheimer molecular dynamics for the charged systems assuming vertical transitions to the charged states at zero temperature, to rationalize the low temperature activation energies, which are found in experiment for chlorobenzene. Our calculations suggest very similar low temperature activation energies for toluene and benzene. For the cationic resonance transitions to physisorption are found even at 0 K, while the anion remains chemisorbed during the propagations. Further, we also extend our previous static quantum chemical investigations to toluene and benzene. In addition, an in depth analysis of the ionization potentials and electron affinities, which are used to estimate resonance energies, is given.}, language = {en} } @phdthesis{Utecht2015, author = {Utecht, Manuel Martin}, title = {Zur Optimierung und dem Auslesen molekularer Schalter}, school = {Universit{\"a}t Potsdam}, pages = {143}, year = {2015}, language = {de} } @misc{SchulzeUtechtMoldtetal.2015, author = {Schulze, Michael and Utecht, Manuel Martin and Moldt, Thomas and Przyrembel, Daniel and Gahl, Cornelius and Weinelt, Martin and Saalfrank, Peter and Tegeder, Petra}, title = {Nonlinear optical response of photochromic azobenzene-functionalized self-assembled monolayers}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-81198}, year = {2015}, abstract = {The combination of photochromic and nonlinear optical (NLO) properties of azobenzene-functionalized self-assembled monolayers (SAMs) constitutes an intriguing step towards novel photonic and optoelectronic devices. By utilizing the second-order NLO process of second harmonic generation (SHG), supported by density-functional theory and correlated wave function method calculations, we demonstrate that the photochromic interface provides the necessary prerequisites en route towards possible future technical applications: we find a high NLO contrast on the order of 16\% between the switching states. These are furthermore accessible reversibly and with high efficiencies in terms of cross sections on the order of 10-18 cm2 for both photoisomerization reactions, i.e., drivable by means of low-power LED light sources. Finally, both photostationary states (PSSs) are thermally stable at ambient conditions.}, language = {en} } @article{SchulzeUtechtMoldtetal.2015, author = {Schulze, Michael and Utecht, Manuel Martin and Moldt, Thomas and Przyrembel, Daniel and Gahl, Cornelius and Weinelt, Martin and Saalfrank, Peter and Tegeder, Petra}, title = {Nonlinear optical response of photochromic azobenzene-functionalized self-assembled monolayers}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {17}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {27}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c5cp03093e}, pages = {18079 -- 18086}, year = {2015}, abstract = {The combination of photochromic and nonlinear optical (NLO) properties of azobenzene-functionalized self-assembled monolayers (SAMs) constitutes an intriguing step towards novel photonic and optoelectronic devices. By utilizing the second-order NLO process of second harmonic generation (SHG), supported by density-functional theory and correlated wave function method calculations, we demonstrate that the photochromic interface provides the necessary prerequisites en route towards possible future technical applications: we find a high NLO contrast on the order of 16\% between the switching states. These are furthermore accessible reversibly and with high efficiencies in terms of cross sections on the order of 10(-18) cm(2) for both photoisomerization reactions, i.e., drivable by means of low-power LED light sources. Finally, both photostationary states (PSSs) are thermally stable at ambient conditions.}, language = {en} } @article{SchulzeUtechtMoldtetal.2015, author = {Schulze, Michael and Utecht, Manuel Martin and Moldt, Thomas and Przyrembel, Daniel and Gahl, Cornelius and Weinelt, Martin and Saalfrank, Peter and Tegeder, Petra}, title = {Nonlinear optical response of photochromic azobenzene-functionalized self-assembled monolayers}, series = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies}, volume = {27}, journal = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies}, number = {17}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c5cp03093e}, pages = {18079 -- 18086}, year = {2015}, abstract = {The combination of photochromic and nonlinear optical (NLO) properties of azobenzene-functionalized self-assembled monolayers (SAMs) constitutes an intriguing step towards novel photonic and optoelectronic devices. By utilizing the second-order NLO process of second harmonic generation (SHG), supported by density-functional theory and correlated wave function method calculations, we demonstrate that the photochromic interface provides the necessary prerequisites en route towards possible future technical applications: we find a high NLO contrast on the order of 16\% between the switching states. These are furthermore accessible reversibly and with high efficiencies in terms of cross sections on the order of 10-18 cm2 for both photoisomerization reactions, i.e., drivable by means of low-power LED light sources. Finally, both photostationary states (PSSs) are thermally stable at ambient conditions.}, language = {en} }