The QChember Project

General Public License version 3.0 (GPL-v3.0)
Copyright © 2025-2026, Prajval K

A proof-of-concept/testing playground for "unconventional" methods in quantum chemistry.

Features

• DFT Grid based 3c2e, 2c2e, 2c1e integrations over Slater-type orbitals
• STO-based RI-RHF and RI-MP2 driver code testing the integration routines (currently builds the full 3c tensor)
• GTO-based RHF powered by libcint over any basis set (currently builds the full ERI tensor)
• OpenMP and SIMD acceleration for integration routines
• Automatic building of auxiliary basis sets
• Direct STO basis set optimization using CMA-ES

Planned Features/Tests

• STO Optimization using GTO, and STO-GTO Hybrid integrals
  • Fernández Rico, J., López, R., Ramírez, G., & Ema, I. (2001). Correspondence between GTO and STO molecular basis sets. Journal of Computational Chemistry, 22(14), 1655–1665. https://doi.org/10.1002/jcc.1121
• Transcorrelated Methods
  • Lee, N., & Thom, A. J. W. (2023). Studies on the Transcorrelated Method. Journal of Chemical Theory and Computation, 19(17), 5743–5759. https://doi.org/10.1021/acs.jctc.3c00046
  • Ochi, M. (2023). Fully self-consistent optimization of the Jastrow-Slater-type wave function using a similarity-transformed Hamiltonian. Physical Review A, 108(3). https://doi.org/10.1103/physreva.108.032806
• Molecular Hamiltonians using Bispinorbitals
  • Novosadov, B. K. (2023). A New Development in Theory of Multielectron Systems. In Advances in Geochemistry, Analytical Chemistry, and Planetary Sciences (pp. 573–578). Springer International Publishing. https://doi.org/10.1007/978-3-031-09883-3_38

Dependencies

• boost::math (https://github.com/boostorg/math)
• cpptrace (https://github.com/jeremy-rifkin/cpptrace)
• IntegratorXX (https://github.com/wavefunction91/IntegratorXX)
• libcint/qcint (https://github.com/sunqm/libcint, https://github.com/sunqm/qcint)
• spdlog (https://github.com/gabime/spdlog)
• wigner-cpp (https://github.com/hydeik/wigner-cpp)
• xsimd (https://github.com/xtensor-stack/xsimd)

Basis sets taken from,

• A New Basis Set Exchange: An Open, Up-to-date Resource for the Molecular Sciences Community. Benjamin P. Pritchard, Doaa Altarawy, Brett Didier, Tara D. Gibson, Theresa L. Windus. J. Chem. Inf. Model. 2019, 59(11), 4814-4820, https://10.1021/acs.jcim.9b00725.
• Ema, I., García de la Vega, J. M., Ramírez, G., López, R., Fernández Rico, J., Meissner, H., & Paldus, J. (2003). Polarized basis sets of Slater‐type orbitals: H to Ne atoms. Journal of Computational Chemistry, 24(7), 859–868. https://doi.org/10.1002/jcc.10227

Documentation and Examples

TBD

Contact

Please let me know if you wish to collaborate,
Prajval K
Masters Student
Indian Institute of Science and Education Research, Thiruvananthapuram
https://prajvalk.me
[email protected], [email protected]