Embedded Cluster Approach and Non-adiabatic Processes

01.06.2010 - 30.06.2019
Forschungsförderungsprojekt
High-level wavefunction based methods will be employed within the framework of an embedded cluster approach (ECA) to study strongly localized defects and excitations in solids and at surfaces as well as the ensuing dynamical processes on fast timescales. The ECA allows the implementation of state-of-the-art quantum mechanical techniques beyond mean-field descriptions to scenarios where correlation effects in excited states are crucial and where the Born-Oppenheimer approximation, the foundation of most quantum mechanical simulations, breaks down. The strength of high-level quantum chemistry methodology such as multi-reference configuration interaction (MRCI) and multi-configuration self-consistent field (MCSCF) methods lies in the ability to account for strong correlations of localized electrons. Its application has been typically limited to relatively small molecules in view of the unfavorable, generally exponential scaling with size. This barrier can be overcome on an approximate level by embedding the active cluster into a matrix of a larger finite or extended system. First applications to wide-band insulators indicate that properties of extended systems such as the valence band structure can be accurately represented for computationally realistic sizes of embedded clusters. This opens up new opportunities to simulate the correlated dynamics of localized defects, excitons, trionic excitations, and excited-state relaxation in clusters, surfaces and solids. As a long-term goal we aim at full dynamical simulations starting with the primary excitation process, following the evolution of the coherently excited many-body electronic state and its relaxation. This requires the implementation of non-adiabatic couplings between energy hypersurfaces within the framework of ¿on-the fly¿ surface hopping dynamics and with an open quantum system (OQS) approach, the quantum trajectory Monte Carlo (QTMC) method, to account for environmental degrees of freedom. During the first four years we will focus on: ¿ Benchmarking the ECA against state-of the art DFT and post-DFT methods for extended systems applied to localized excitations in wide-band gap insulators. ¿ Computation of accurate reference data and determination of effective tight- binding parameters for structural defects, local edge disorder and adsorbates. ¿ Integrating the ECA, non-adiabatic dynamics, and QTMC methods. ¿ Simulating non-adiabatic processes in charged-particle-alkalihalide scattering and photo- and defect dynamics in DNA.

Personen

Projektleiter_in

Projektmitarbeiter_innen

Institut

Grant funds

  • FWF - Österr. Wissenschaftsfonds (National) Stand-Alone Project Austrian Science Fund (FWF)

Forschungsschwerpunkte

  • Quantum many-body systems: 100%

Schlagwörter

DeutschEnglisch
QuantenchemieQuantum chemistry
EingebettetEmbedding

Externe Partner_innen

  • Universität Wien

Publikationen