Molecular Materials and Organic Electronics
One major research theme in the group will be concerned with molecular materials and organic electronics. I have been previously involved in several such projects studying a wide variety of molecular structures:
- thiophene based molecules with potential for OLED applications [12,37]
- solvatochromic effects  and two-photon absorption  in push-pull systems,
- PPV (p-phenylene vinylene) oligomers with applications in photovoltaics [11,27],
- other conjugated polymers [26,38],
- open-shell character in graphene nanoribbons of various types [10,16,30,39],
- transition metal complexes [22,46],
- dynamics of electronic energy transfer in a molecular dyad  and the benzene dimer , and
- excited-state intramolecular proton transfer [1,2,5].
Excited states of interacting nucleobases
It has been a constant interest of mine to study the photophysics and charge transfer properties of DNA and how they are affected by stacking and base pairing. For reviews of computations on these systems, consider Refs [21,33]. We have performed detailed work on the UV absorbing states in single  and double-stranded DNA , showing that nearest-neighbour interactions between nucleobases play a role but that electronic delocalization does not exceed two or three nucleobases. These results were based on a new analysis strategy for the one-electron transition density matrix . Furthermore, exciplex formation in the adenine dinucleotide was examined . An initial project was concerned with charge transfer in stacked π-systems. The ethylene dimer radical cation with a bridge of up to three formaldehyde molecules proved to be an excellent model system to examine the basic physics of charge transfer . Based on this experience a more extended study of energy transfer and proton-coupled electron transfer in the 2-pyridone dimer radical cation was performed .
The TheoDORE (Theoretical Density, Orbital Relaxation, and Exciton) analysis package is a diverse and flexible wavefunction analysis suite developed and maintained by F. Plasser. Aside from different population analysis methods and the natural transition orbital decomposition, special features of TheoDORE are concerned with
- electron-hole correlation plots  and conditional electron densities  to visualize static correlation in the excited state ,
- natural difference orbitals showing orbital relaxation [18,17],
- computation of an approximate exciton size [20,27],
- an entanglement analysis ,
- the analysis of unpaired electrons , and
- analysis tools for transition metal complexes [22,46].
The wavefunction analysis library libwfa is a parallel development to TheoDORE, allowing to do wavefunction analysis in an integrated fashion. The main enhancments as compared to TheoDORE are
- multipole analysis of exciton wavefunctions to allow the computation of exciton sizes in real space and correlation coefficients [20,24],
- exciton binding energies (in progress),
- an entanglement analysis , and
- enhanced plotting capabilities.
Currently, libwfa is interface to the Q-Chem and Molcas program packages. Feel free to contact me or another developer if you are interested in interfacing libwfa to your own code.
- Improving the efficiency of parallel MR-CI calculations with a special focus on non-adiabatic dynamics simulations.
- Maintaining and expanding the interface to the MOLCAS code .
- Controlling the work-flow in parallel MR-CI calculations to allow for user-friendly utilization of the newly devoloped program code. For applications see Refs [10,16,30].
- Local MR-CI .
- Enhancing the efficiency of the computation of gradients and non-adiabatic couplings at the state averaged multi-configuration self-consistent field method to allow for non-adiabatic dynamics simulations of systems of signficantly increased size. In particular the computation of the non Hellmann-Feynman terms has been sped up.
- Interfacing of different modules to allow for an efficient calculation of spin-orbit coupling elements to be used for non-adiabatic dynamics simulations .
- Providing an efficient and flexible way to interface to the various functionalities of COLUMBUS, in particular in connection with dynamics simulations and QM/MM hybrid treatment (through work on the runc execution script and the colinp interactive input facility). In particular I am working on some of the input tools to speed up user input without losing flexibility in the input options.
- User registration and distribution of the COLUMBUS code.
- Maintaining and expanding the interface to the COLUMBUS program package .
- Implementation of new wavefunction analysis methods through the wavefunction analysis library libwfa .
Q-CHEM is a comprehensive ab-initio quantum chemistry package with a wide range of electronic structure methods implemented. My work is concerned with excited state analysis methods
- Density matrix based analysis and visualization methods implemented for the ADC method [18,17] providing deeper insight into excited state structure including an analysis of the transition density matrix for the visualization of electron-hole correlations  and an attachment/detachment density analysis.
- The same analysis for time-dependent density functional theory calculations with a focus on dynamic charge transfer effects .
- Comparison of the ADC, EOM-CC, and TDDFT methods .
- Implementation of local diabatization a stable way of integrating the time-dependent electronic Schrödinger equation .
- ADC(2) non-adiabatic couplings and general maintenance of the wavefunction overlap code .
- Normal mode analysis and Essential Dynamics to be able to follow and analyze molecular motions. For more details see my Diploma Thesis (Sec. 2.3.4), for applications consider Refs [1,8].
- Interface to COLUMBUS 7.0.
- Interface to DFTB+ .
SHARC (Surface Hopping including Arbitrary Couplings) is a software suite used for the simulation of non-adiabatic molecular dynamics. Aside from standard photodynamics, it allows for the simulation of intersystem crossing and explicit interactions with a radiation field. My work is concerned with
- The efficient computation of wavefunction overlaps as needed for non-adiabatic dynamics simulations  (Download). Application of the same code for wavefunction comparisons  and parameterization of vibronic coupling models .
- Surface hopping with correlated single-reference methods .
- Highly efficient surface hopping dynamics using vibronic coupling models .
- Surface hopping dynamics within an exciton model .
- Decoherence corrections and momentum rescaling.
 F. Plasser: “Visualisation of Electronic Excited-State Correlation in Real Space”. ChemPhotoChem (2019).
 S. Mai, F. Plasser, P. Marquetand, L. González: “General trajectory surface hopping method for ultrafast nonadiabatic dynamics”. In M. J. J. Vrakking, F. Lepine (editors), Attosecond Molecular Dynamics, Theoretical and Computational Chemistry Series, The Royal Society of Chemistry (2019).
 T. M. Cardozo, A. P. Galliez, I. Borges Jr, F. Plasser, A. Aquino, M. Barbatti, H. Lischka: “Dynamics of Benzene Excimer Formation from the Parallel-Displaced Dimer”. PCCP (2019).
 F. Plasser, S. Gómez, M. F. S. J. Menger, S. Mai, L. González: “Highly efficient surface hopping dynamics using a linear vibronic coupling model”. PCCP, 21, 57-59 (2019).
— 2018 —
 M. F. S. J. Menger, F. Plasser, B. Mennucci, L. González: “Surface hopping within an exciton picture – An electrostatic embedding scheme”. J. Chem. Theory Comput., 14, 6139-6148 (2018).
 H. Lischka, D. Nachtigallová, A. J. A. Aquino, P. Szalay, F. Plasser, F. B. C. Machado, M. Barbatti: “Multireference Approaches for Excited States of Molecules”. Chem. Rev., 118, 7293-7361 (2018).
 M. Tromayer, P. Gruber, A. Rosspeintner, A. Ajami, W. Husinsky, F. Plasser, L. González, E. Vauthey, A. Ovsianikov, R. Liska: “Wavelength-optimized Two-Photon Polymerization Using Initiators Based on Multipolar Aminostyryl-1,3,5-triazines”. Sci. Rep., 8, 17 273 (2018).
 M. Fumanal, F. Plasser, S. Mai, C. Daniel, E. Gindensperger: “Interstate Vibronic Coupling Constants Between Electronic Excited States for Complex Molecules”. J. Chem. Phys., 148, 124 119 (2018).
 S. A. Mewes, F. Plasser, A. Krylov, A. Dreuw: “Benchmarking Excited-State Calculations Using Exciton Properties”. J. Chem. Theory Comput., 14, 710-725 (2018).
 S. Mai, F. Plasser, J. Dorn, M. Fumanal, C. Daniel, L. González: “Quantitative wave function analysis for excited states of transition metal complexes”. Coord. Chem. Rev., 361, 74-97 (2018).
— 2017 —
 L. Stojanović, S. Aziz, R. Hilal, F. Plasser, T. Niehaus, M. Barbatti: “Nonadiabatic Dynamics of Cycloparaphenylenes with TD-DFTB Surface Hopping”. J. Chem. Theory Comput., 13, 5846-5860 (2017).
 S. Mai, F. Plasser, M. Pabst, F. Neese, A. Köhn, L. González: “Surface hopping dynamics including intersystem crossing using the algebraic diagrammatic construction method”. J. Chem. Phys., 147, 184109 (2017).
 F. Plasser, S. Mewes, A. Dreuw, L. González: “Detailed Wave Function Analysis for Multireference Methods: Implementation in the Molcas Program Package and Applications to Tetracene”. J. Chem. Theory Comput., 13, 5343-5353 (2017).
 T. Rosenau, A. Potthast, N. Zwirchmayr, H. Hettegger, F. Plasser, T. Hosoya, M. Bacher, K. Krainz, T. Dietz: “Chromophores from hexeneuronic acids: identification of HexA-derived chromophores”. Cellulose, 24, 3671-3687 (2017).
 J. Nogueira, F. Plasser, L. González: “Electronic delocalization, charge transfer and hypochromism in the UV absorption spectrum of polyadenine unravelled by multiscale computations and quantitative wavefunction analysis”. Chem. Sci., 8, 5682-5691 (2017).
 P. Kautny, F. Glöcklhofer, T. Kader, J. Mewes, B. Stöger, J. Fröhlich, D. Lumpi, F. Plasser: “Charge-transfer states in triazole linked donor-acceptor materials: Strong effects of chemical modification and solvation”. PCCP, 19, 18 055-18 067 (2017).
 A. Das, T. Müller, F. Plasser, D. Krisiloff, E. Carter, H. Lischka: “Local Electron Correlation Treatment in Extended Multireference Calculations: Effect of Acceptor-Donor Substituents on the Biradical Character of the Polycyclic Aromatic Hydrocarbon Heptazethrene”. J. Chem. Theory Comput., 13, 2612-2622 (2017).
 S. Mewes, F. Plasser, A. Dreuw: “Universal Exciton Size in Organic Polymers is Determined by Nonlocal Orbital Exchange in Time-Dependent Density Functional Theory”. J. Phys. Chem. Lett., 8, 1205-1210 (2017).
 B. Holzer, J. Bintinger, D. Lumpi, C. Choi, Y. Kim, B. Stöger, C. Hametner, M. Marchetti-Deschmann, F. Plasser, E. Horkel, I. Kymissis, J. Fröhlich: “Color Fine-Tuning of Optical Materials Through Rational Design”. ChemPhysChem, 18, 549-563 (2017).
 C. Wiebeler, F. Plasser, G. Hedley, A. Ruseckas, I. Samuel, S. Schumacher: “Ultrafast Electronic Energy Transfer in an Orthogonal Molecular Dyad”. J. Phys. Chem. Lett., 8, 1086-1092 (2017).
 A. Luzanov, F. Plasser, A. Das, H. Lischka: “Evaluation of the quasi correlated tight-binding (QCTB) model for describing polyradical character in polycyclic hydrocarbons”. J. Chem. Phys., 146, 064106 (2017).
 S. Chopra, F. Plasser: “Uv absorption inmetal decorated boron nitride flakes: A theoretical analysis of excited states”. Mol. Phys., 115, 2469-2477 (2017).
 P. Marquetand, J. Nogueira, S. Mai, F. Plasser, L. González: “Challenges in simulating light-induced processes in DNA”. Molecules, 22, 49 (2017).
— 2016 —
 F. Plasser, L. González: “Communication: Unambiguous comparison of many-electron wavefunctions through their overlaps”. J. Chem. Phys., 145, 021103 (2016).
 F. Plasser: “Entanglement entropy of electronic excitations”. J. Chem. Phys., 144, 194107 (2016).
 A. Das, T. Müller, F. Plasser, H. Lischka: “Polyradical Character of Triangular Non-Kekulé Structures, Zethrenes, p-Quinodimethane-Linked Bisphenalenyl, and the Clar Goblet in Comparison: An Extended Multireference Study”. J. Phys. Chem. A, 120, 1625-1636 (2016).
 F. Plasser, M. Ruckenbauer, S. Mai, M. Oppel, P. Marquetand, L. González: “Efficient and Flexible Computation of Many-Electron Wave Function Overlaps”. J. Chem. Theory Comput., 12, 1207-1219 (2016).
 F. Aquilante, J. Autschbach, R. Carlson, L. Chibotaru, M. Delcey, L. De Vico, I. Fdez Galván, N. Ferré, L. Frutos, L. Gagliardi, M. Garavelli, A. Giussani, C. Hoyer, G. Li Manni, H. Lischka, D. Ma, P. Malmqvist, T. Müller, A. Nenov, M. Olivucci, T. Pedersen, D. Peng, F. Plasser, B. Pritchard, M. Reiher, I. Rivalta, I. Schapiro, J. Segarra-MartÃ, M. Stenrup, D. Truhlar, L. Ungur, A. Valentini, S. Vancoillie, V. Veryazov, V. Vysotskiy, O. Weingart, F. Zapata, R. Lindh: “Molcas 8: New capabilities for multiconfigurational quantum chemical calculations across the periodic table”. J. Comp. Chem., 37, 506-541 (2016).
 S. Mewes, J. Mewes, A. Dreuw, F. Plasser: “Excitons in poly(para phenylene vinylene): a quantum-chemical perspective based on high-level ab initio calculations”. PCCP, 18, 2548-2563 (2016).
— 2015 —
 S. Kraner, R. Scholz, F. Plasser, C. Koerner, K. Leo: “Exciton size and binding energy limitations in one-dimensional organic materials”. J. Chem. Phys., 143, 244905 (2015).
 S. Mewes, F. Plasser, A. Dreuw: “Communication: Exciton analysis in time-dependent density functional theory: How functionals shape excited-state characters”. J. Chem. Phys., 143, 171101 (2015).
 F. Plasser, B. Thomitzni, S. Bäppler, J. Wenzel, D. Rehn, M. Wormit, A. Dreuw: “Statistical analysis of electronic excitation processes: Spatial location, compactness, charge transfer, and electron-hole correlation”. J. Comp. Chem., 36, 1609-1620 (2015).
 I. Georgieva, A. Aquino, F. Plasser, N. Trendafilova, A. Köhn, H. Lischka: “Intramolecular Charge-Transfer Excited-State Processes in 4-(N, N -Dimethylamino)benzonitrile: The Role of Twisting and the πσ* State”. J. Phys. Chem. A, 119, 6232-6243 (2015).
 F. Plasser, A. Dreuw: “High-level ab initio computations of the absorption spectra of organic iridium complexes”. J. Phys. Chem. A, 119, 1023-1036 (2015).
 F. Plasser, A. Aquino, H. Lischka, D. Nachtigallová: “Electronic excitation processes in single-strand and double-strand DNA: A computational approach”. volume 356, 1-38 (2015).
— 2014 —
 S. Bäppler, F. Plasser, M. Wormit, A. Dreuw: “Exciton analysis of many-body wave functions: Bridging the gap between the quasiparticle and molecular orbital pictures”. Phys. Rev. A, 90, 052521 (2014).
 S. Mai, T. Müller, F. Plasser, P. Marquetand, H. Lischka, L. González: “Perturbational treatment of spin-orbit coupling for generally applicable high-level multi-reference methods”. J. Chem. Phys., 141, 074105 (2014).
 F. Plasser, S. Bäppler, M. Wormit, A. Dreuw: “New tools for the systematic analysis and visualization of electronic excitations. II. Applications”. J. Chem. Phys., 141, 024107 (2014).
 F. Plasser, M. Wormit, A. Dreuw: “New tools for the systematic analysis and visualization of electronic excitations. I. Formalism”. J. Chem. Phys., 141, 024106 (2014).
 S. Horn, F. Plasser, T. Müller, F. Libisch, J. Burgdörfer, H. Lischka: “A comparison of singlet and triplet states for one- and two-dimensional graphene nanoribbons using multireference theory”. Theor. Chem. Acc., 133, 1-9 (2014).
 F. Plasser, R. Crespo-Otero, M. Pederzoli, J. Pittner, H. Lischka, M. Barbatti: “Surface hopping dynamics with correlated single-reference methods: 9H-adenine as a case study”. J. Chem. Theory Comput., 10, 1395-1405 (2014).
 Z. Cui, H. Lischka, T. Mueller, F. Plasser, M. Kertesz: “Study of the diradicaloid character in a prototypical pancake-bonded dimer: The stacked tetracyanoethylene (TCNE) anion dimer and the neutral K2TCNE2 complex”. ChemPhysChem, 15, 165-175 (2014).
 M. Barbatti, M. Ruckenbauer, F. Plasser, J. Pittner, G. Granucci, M. Persico, H. Lischka: “Newton-X: A surface-hopping program for nonadiabatic molecular dynamics”. WIREs: Comp. Mol. Sci., 4, 26-33 (2014).
— 2013 —
 D. Lumpi, E. Horkel, F. Plasser, H. Lischka, J. Fröhlich: “Synthesis, spectroscopy, and computational analysis of photoluminescent bis(aminophenyl)-substituted thiophene derivatives”. ChemPhysChem, 14, 1016-1024 (2013).
 A. Panda, F. Plasser, A. Aquino, I. Burghardt, H. Lischka: “Electronically excited states in poly(p-phenylenevinylene): Vertical excitations and torsional potentials from high-level Ab initio calculations”. J. Phys. Chem. A, 117, 2181-2189 (2013).
 F. Plasser, H. Pasalic, M. Gerzabek, F. Libisch, R. Reiter, J. Burgdörfer, T. Müller, R. Shepard, H. Lischka: “The multiradical character of one- and two-dimensional graphene nanoribbons”. Angew. Chem., 52, 2581-2584 (2013).
 F. Plasser, H. Lischka: “Electronic excitation and structural relaxation of the adenine dinucleotide in gas phase and solution”. Photochemical and Photobiological Sciences, 12, 1440-1452 (2013).
— 2012 —
 F. Plasser, G. Granucci, J. Pittner, M. Barbatti, M. Persico, H. Lischka: “Surface hopping dynamics using a locally diabatic formalism: Charge transfer in the ethylene dimer cation and excited state dynamics in the 2-pyridone dimer”. J. Chem. Phys., 137, 22A514 (2012).
 F. Plasser, A. Aquino, W. Hase, H. Lischka: “UV absorption spectrum of alternating DNA duplexes. Analysis of excitonic and charge transfer interactions”. J. Phys. Chem. A, 116, 11 151-11 160 (2012).
 F. Plasser, H. Lischka: “Analysis of excitonic and charge transfer interactions from quantum chemical calculations”. J. Chem. Theory Comput., 8, 2777-2789 (2012).
 N. Kungwan, F. Plasser, A. Aquino, M. Barbatti, P. Wolschann, H. Lischka: “The effect of hydrogen bonding on the excited-state proton transfer in 2-(2′-hydroxyphenyl)benzothiazole: A TDDFT molecular dynamics study”. PCCP, 14, 9016-9025 (2012).
 F. Plasser, M. Barbatti, A. Aquino, H. Lischka: “Electronically excited states and photodynamics: A continuing challenge”. Theor. Chem. Acc., 131, 1-14 (2012).
— 2011 —
 F. Plasser, H. Lischka: “Semiclassical dynamics simulations of charge transport in stacked -systems”. J. Chem. Phys., 134, 034309 (2011).
— 2009 —
 A. Aquino, F. Plasser, M. Barbatti, H. Lischka: “Ultrafast excited-state proton transfer processes: Energy surfaces and on-the-fly dynamics simulations”. Croatica Chemica Acta, 82, 105-114 (2009).
 F. Plasser, M. Barbatti, A. Aquino, H. Lischka: “Excited-state diproton transfer in bipyridyldiol: The mechanism is sequential, not concerted”. J. Phys. Chem. A, 113, 8490-8499 (2009).