MP2-libint2

A minimal implementation of second-order Møller-Plesset perturbation theory (MP2) based on the Libint2 integral library. This project is intended for learning and experimenting with quantum chemistry programming, including Hartree-Fock, AO integrals, AO-MO transformation, and MP2 energy evaluation.

This is the developing branch, which contains an actively evolving implementation with modularized code structure and experimental features.

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Features

Current capabilities include:

• Gaussian basis integral evaluation using Libint2
• Restricted Hartree-Fock (RHF) framework
• AO to MO integral transformation
• MP2 correlation energy calculation
• Modular structure suitable for learning and extension
• Simple Makefile-based build system
• Example molecular geometry files (.xyz), output files (.out) and Gaussian 16 results (.log)

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Project Structure

.
├── main.cpp          # Program entry point
├── integrals.cpp     # AO integral and MP2 energy evaluation using Libint2
├── ao2mo.cpp         # AO to MO integral transformation
├── hartree_fock.h    # Hartree-Fock related definitions
├── linalg.cpp        # Linear algebra utilities
├── globals.cpp       # Global variables and shared data
├── utils.cpp         # Utility functions
├── Makefile          # Build configuration
├── h2o.xyz           # Example molecule: water
├── DPPBz.xyz         # Example molecule: DPPBz
└── test/             # Test files and results

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Dependencies

You must install the following dependencies:

Required:

• C++ compiler supporting C++11 or later (g++, clang++)
• Libint2
• Eigen

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Installing Libint2

see https://github.com/evaleev/libint

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Build Instructions

modify the libint2 and Eigen path in Makefile and compile using:

make

This produces the executable:

MP2

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Running the Program

set parallelism

export LIBINT_NUM_THREADS=20

run example:

./MP2 h2o.xyz aug-cc-pVTZ

or:

./MP2 DPPBz.xyz def2-SVP

The program will:

1. Read molecular geometry
2. Construct basis set
3. Compute AO integrals
4. Perform Hartree-Fock calculation
5. Transform integrals to MO basis
6. Compute MP2 correlation energy

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License

This project uses Libint2, which is distributed under GPL/LGPL licenses.

See:

LICENSE
COPYING

for details.

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Author

Xiaoyi Zhai

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Acknowledgements

• Libint2 by Edward F. Valeev
• Quantum chemistry open source community

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Notes

This code is intended primarily for educational and research learning purposes, not production-level calculations.