🚀 QUESTDB: A Database of Highly-Accurate Excitation Energies

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📚 Table of Contents

• ✨ Key Features
• 🧪 Why Use QUESTDB?
• 📂 Repository Contents
• 👥 Contributors
• 📚 Main References
• 📖 Other References
• 🔋 Extension to Charged Excitations
• 🗂️ Data Structure
• 💰 Funding
• 🧮 HPC resources

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✨ Key Features

• 🔬 High Accuracy:
  Data obtained using state-of-the-art methods (FCI, CC3, CCSDT, CCSDTQ, CC4, CASPT2/3, NEVPT2, etc.)

• 🌍 Wide Chemical Coverage:
  Includes small molecules, radicals, charged species, and transition metal complexes.

• 🎯 Challenging Excitations:
  Focus on double excitations and intramolecular charge-transfer (CT) states.

• 🛠️ Continuously Updated:
  Regularly improved with new high-level calculations and critical assessments.

• 📂 Easy-to-Use Format:
  Organized .xlsx spreadsheets and .json files for simple extraction and analysis.

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🧪 Why Use QUESTDB?

QUESTDB supports researchers to:

• Benchmark TD-DFT, wavefunction-based, and emerging excited-state methods.
• Guide the development of new computational models.
• Facilitate interpretation of experimental spectra and photochemistry.

Note: Our vision is to establish QUESTDB as a cornerstone resource for benchmarking and training the next generation of AI-driven models in excited-state science.

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⚙️ Scripts for Subset Generation and Analysis

This repository includes Python scripts to help users generate representative "diet" subsets of QUEST excitation energies—for instance, sets of 50, 100, or 200 transitions that reproduce the statistical properties of the full database (e.g., MAE, MSE, and RMSE) across different computational methods and excitation categories (see the data/diet directory).

These tools are especially useful for benchmarking new methods quickly or for training machine learning models when computational cost is a limiting factor.

Main functionalities include:

• ✅ Generation of optimized subsets matching the full dataset’s distribution across:
  • Spin states
  • Valence vs Rydberg states
  • Excitation types (e.g., nπ*, ππ*, etc.)
  • Molecule sizes or other custom filters
• ✅ Support for flexible user-defined filters (e.g., only valence, only singlets, exclude genuine doubles)
• ✅ Preservation of full metadata in output JSON files
• ✅ Optional optimization of subset selection using a genetic algorithm with Bayesian hyperparameter tuning (via optuna)

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📂 Repository Contents

This repository provides:

• Molecular Structures
• Vertical Excitation Energies
• Oscillator Strengths
• Many Other Properties

Data is structured in .xlsx and .json files for ease of use (see the data directory).

📌 See the accompanying paper:
The QUEST database of highly-accurate excitation energies
P.-F. Loos, M. Boggio-Pasqua, A. Blondel, F. Lipparini, and D. Jacquemin,
J. Chem. Theory Comput. 21, 8010 (2025). DOI:10.1021/acs.jctc.5c00975

<img src="TOC.jpg" width="250"> © Béatrice Lejeune (@bea_quarelle)

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👥 Contributors

The QUESTDB project is maintained by a collaboration between:

• Denis Jacquemin (Nantes)
• Pierre-François Loos (Toulouse)
• Martial Boggio-Pasqua (Toulouse)
• Fábris Kossoski (Toulouse)
• Filippo Lipparini (Pisa)
• Anthony Scemama (Toulouse)
• Aymeric Blondel (Nantes)
• Mickael Véril (Toulouse)
• Yann Damour (Toulouse)
• Antoine Marie (Toulouse)

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📚 Main References

Review articles on the QUEST database:

• The QUEST database of highly-accurate excitation energies
  P.-F. Loos, M. Boggio-Pasqua, A. Blondel, F. Lipparini, and D. Jacquemin,
  J. Chem. Theory Comput. 21, 8010 (2025).

• QUESTDB: a database of highly-accurate excitation energies for the electronic structure community
  M. Véril, A. Scemama, M. Caffarel, F. Lipparini, M. Boggio-Pasqua, D. Jacquemin, and P.-F. Loos,
  WIREs Comput. Mol. Sci. 11, e1517 (2021).

• The quest for highly accurate excitation energies: a computational perspective
  P.-F. Loos, A. Scemama, and D. Jacquemin,
  J. Phys. Chem. Lett. 11, 2374 (2020).

Key QUESTDB publications:

• Reference energies for double excitations: improvement & extension
  F. Kossoski, M. Boggio-Pasqua, P.-F. Loos, and D. Jacquemin,
  J. Chem. Theory Comput. 20, 5655 (2024).

• Reference vertical excitation energies for transition metal compounds
  D. Jacquemin, F. Kossoski, F. Gam, M. Boggio-Pasqua, and P.-F. Loos,
  J. Chem. Theory Comput. 19, 8782 (2023).

• A mountaineering strategy to excited states: revising reference values with EOM-CC4
  P.-F. Loos, F. Lipparini, D. A. Matthews, A. Blondel, and D. Jacquemin,
  J. Chem. Theory Comput. 18, 4418 (2022).

• A mountaineering strategy to excited states: highly-accurate energies and benchmarks for bicyclic systems
  P.-F. Loos and D. Jacquemin,
  J. Phys. Chem. A 125, 10174 (2021).

• Reference energies for intramolecular charge-transfer excitations
  P.-F. Loos, M. Comin, X. Blase, and D. Jacquemin,
  J. Chem. Theory Comput. 17, 3666 (2021).

• A mountaineering strategy to excited states: highly-accurate oscillator strengths and dipole moments of small molecules
  A. Chrayteh, A. Blondel, P.-F. Loos, and D. Jacquemin,
  J. Chem. Theory Comput. 17, 416 (2021).

• A mountaineering strategy to excited states: highly-accurate energies and benchmarks for exotic molecules and radicals
  P.-F. Loos, A. Scemama, M. Boggio-Pasqua, and D. Jacquemin,
  J. Chem. Theory Comput. 16, 3720 (2020).

• A mountaineering strategy to excited states: highly-accurate energies and benchmarks for medium size molecules
  P.-F. Loos, F. Lipparini, M. Boggio-Pasqua, A. Scemama, and D. Jacquemin,
  J. Chem. Theory Comput. 16, 1711 (2020).

• Reference energies for double excitations
  P.-F. Loos, M. Boggio-Pasqua, A. Scemama, M. Caffarel, and D. Jacquemin,
  J. Chem. Theory Comput. 15, 1939 (2019).

• A mountaineering strategy to excited states: highly-accurate reference energies and benchmarks
  P.-F. Loos, A. Scemama, A. Blondel, Y. Garniron, M. Caffarel, and D. Jacquemin,
  J. Chem. Theory Comput. 14, 4360 (2018).

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📖 Other References

• Excited-state absorption: Reference oscillator strengths, wavefunction and TD-DFT benchmarks
  J. Širůček, B. Le Guennic, Y. Damour, P.-F. Loos, and D. Jacquemin,
  J. Chem. Theory Comput. 21, 4688 (2025).

• Reference CC3 excitation energies for organic chromophores: benchmarking TD-DFT, BSE/GW and wave function methods
  I. Knysh, F. Lipparini, I. Duchemin, X. Blase, P.-F. Loos, and D. Jacquemin,
  J. Chem. Theory Comput. 20, 8152 (2024).

• Heptazine, cyclazine, and related compounds: chemically-accurate estimates of the inverted singlet-triplet gap
  P.-F. Loos, F. Lipparini, and D. Jacquemin,
  J. Phys. Chem. Lett. 14, 11069 (2023).

• Ground- and excited-state dipole moments and oscillator strengths of full configuration interaction quality
  Y. Damour, R. Quintero-Monsebaiz, M. Caffarel, D. Jacquemin, F. Kossoski, A. Scemama, and P.-F. Loos,
  J. Chem. Theory Comput. 19, 221 (2023).

• Benchmarking CASPT3 vertical excitation energies
  M. Boggio-Pasqua, D. Jacquemin, and P.-F. Loos,
  J. Chem. Phys. 157, 014103 (2022).

• Reference energies for cyclobutadiene: automerization and excited states
  E. Monino, M. Boggio-Pasqua, A. Sc