iSPECTRON

iSPECTRON simulates linear and nonlinear spectroscopic spectra by parsing ab-initio quantum chemistry outputs and generating inputs for the Spectron code to compute vibronic and electronic spectral properties.

Key Features:

• Quantum chemistry interfaces: Interfaces with NWChem, OpenMolcas, Gaussian and Cobramm to ingest electronic structure data.
• Spectron input generation: Parses quantum chemistry outputs and generates the input files required by the Spectron code.
• Vibronic analysis: Expresses vibronic spectra in terms of electronic eigenstates obtained from quantum chemistry computations.
• Displaced harmonic oscillator model: Incorporates vibrational and bath effects using the displaced harmonic oscillator model.
• Franck-Condon evaluation: Computes all relevant spectroscopic quantities at the Franck-Condon point.
• Spectral modalities: Simulates linear absorption, transient absorption, and two-dimensional electronic spectra.
• Multi-level electronic structure support: Supports TD-DFT calculations via NWChem and RASSCF/RASPT2 via OpenMolcas for comparative studies.

Scientific Applications:

• Linear absorption spectroscopy: Enables computation and analysis of linear absorption spectra from ab-initio electronic structure data.
• Transient absorption spectroscopy: Produces transient absorption spectra for time-resolved electronic spectroscopy studies.
• Two-dimensional electronic spectroscopy: Generates two-dimensional electronic spectra for electronic spectroscopy investigations.
• Method comparison: Facilitates comparative studies between TD-DFT and RASSCF/RASPT2 spectral predictions.
• Example systems: Applied to example studies on the pyrene molecule.

Methodology:

Parses outputs from NWChem, OpenMolcas, Gaussian and Cobramm; generates input files for the Spectron code; expresses vibronic spectra via electronic eigenstates; includes vibrational and bath effects using the displaced harmonic oscillator model; computes quantities at the Franck-Condon point; and supports TD-DFT (NWChem) and RASSCF/RASPT2 (OpenMolcas).