Quiqbox is a quantum chemistry and quantum physics software package that starts around Gaussian basis set optimization for electronic structure problems. Quiqbox is written in pure Julia. This work is supported by the U.S. Department of Energy under Award No. DESC0019374.

Documentation	Digital Object Identifier	Publication	License

Development Status

Features

• Native 1-electron and 2-electron integral functions.
• Floating and fixed-position contracted Gaussian-type orbital (CGTO).
• Mixed-contracted GTO (linear combination of GTOs with mixed centers or orbital angular momentum) as a basis function.
• Restricted (closed-shell) and unrestricted (open-shell) Hartree–Fock methods (RHF & UHF).
• Variational optimization of basis set parameters based on a hybrid analytical differentiation design combining automatic differentiation (AD) and symbolic differentiation (SD).

Setup

OS (64-bit) support

• Generic Linux
• macOS
• Windows

NOTE: Each operating system (OS) platform is only tested on the x86-64 architecture. The support of those systems on different architectures (such as macOS on ARM architecture) is not guaranteed.

Julia (64-bit) compatibility

Quiqbox will always try to support the latest stable release of 64-bit Julia as soon as possible. On the other hand, backward compatibility with previous versions is not guaranteed but can be checked here.

Installation in Julia REPL

Type ] in the default Julian mode to switch to the Pkg mode:

(@v1.x) pkg>

Type the following command and hit Enter key to install Quiqbox:

(@v1.x) pkg> add Quiqbox

After the installation completes, hit the Backspace key to go back to the Julian mode and use using to load Quiqbox:

julia> using Quiqbox

Showcase

Combine atomic orbitals

points = GridBox((1,0,0), 1.4).point

bsH₂ = vcat(genBasisFunc.(points, "STO-3G")...)

Build a customized basis set

gf = GaussFunc(1.0, 0.75)

bs = genBasisFunc.(points, Ref(gf)) .+ bsH₂

Run the Hartree–Fock method

nuc = ["H", "H"]

coords = coordOf.(points)

runHF(bs, nuc, coords)

Optimize the basis set

pars = markParams!(bs, true)

optimizeParams!(pars, bs, nuc, coords)

Documentation

Objects defined by Quiqbox that are directly exported to the user have the corresponding docstring, which can be accessed through the Help mode in Julia REPL. The latest release's documentation contains all the docstrings and additional tutorials of the package. For unreleased/experimental features, please refer to the developer documentation.

Citation

If you use Quiqbox in your research, please cite the following paper:

• Wang, W., & Whitfield, J. D. (2023). Basis set generation and optimization in the NISQ era with Quiqbox.jl. Journal of Chemical Theory and Computation, 19(22), 8032-8052.