Quantum Package 2.0: An Open-Source Determinant-Driven Suite of Programs.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• High-Performance Computing

Background:

• Accurate quantum chemistry calculations require computationally intensive methods with high scaling.
• Approximations and efficient parallel implementations are crucial for chemically meaningful system sizes.
• Existing software often lacks flexibility in handling large determinant spaces and advanced methods.

Purpose of the Study:

• Introduce Quantum Package, an open-source environment for advanced wave function methods in quantum chemistry.
• Develop and implement determinant-driven selected configuration interaction (sCI) and multireference perturbation theory (PT2).
• Facilitate easy implementation and parallel execution of new computational chemistry methods.

Main Methods:

• Utilizes a determinant-driven framework for selected configuration interaction (sCI).
• Implements the CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively) algorithm with PT2 corrections.
• Leverages the IRPF90 code generator for collaborative development and parallelization on supercomputers.

Main Results:

• Quantum Package supports tens of millions of determinants on thousands of CPU cores, scaling to 12,288 cores.
• Introduces a renormalized PT2 correction for efficient extrapolation to the full configuration interaction (CI) limit.
• Presents a novel stochastic CIPSI selection integrated with PT2 calculations, offering computational savings.

Conclusions:

• Quantum Package provides a flexible and efficient platform for high-level quantum chemistry research.
• The new developments significantly improve the accuracy and efficiency of correlated wave function methods.
• The software is designed for ease of use and scalability on modern high-performance computing architectures.