Pythonic Black-box Electronic Structure Tool (PyBEST) represents a fully-fledged modern electronic structure software package developed at Nicolaus Copernicus University in Toruń. The package provides an efficient and reliable platform for electronic structure calculations at the interface between chemistry and physics using unique electronic structure methods, analysis tools, and visualization. Examples are the (orbital-optimized) pCCD-based models for ground- and excited-states electronic structure calculations as well as the quantum entanglement analysis framework based on the single-orbital entropy and orbital-pair mutual information. PyBEST is written primarily in the Python programming language with additional parts written in C＋＋, which are interfaced using Pybind11, a lightweight header-only library. By construction, PyBEST is easy to use, to code, and to interface with other software packages. Moreover, its modularity allows us to conveniently host additional Python packages and software libraries in future releases to enhance its performance. The electronic structure methods available in PyBEST are tested for the half-filled 1-D model Hamiltonian. The capability of PyBEST to perform large-scale electronic structure calculations is demonstrated for the model vitamin B₁₂ compound. The investigated molecule is composed of 190 electrons and 777 orbitals for which an orbital optimization within pCCD and an orbital entanglement and correlation analysis are performed for the first time.

Program summary

Program title: PyBEST

CPC Library link to program files: https://doi.org/10.17632/xf9kb7yfwr.1

Developer’s repository link: https://zenodo.org/record/3925278#.X5KAZS8Rq6s

Licensing provisions: GNU General Public License 3

Programming language: Python, C＋＋

Nature of problem: Efficient and reliable modeling of electronic structures featuring both weakly- and strongly-correlated electrons. Small- and large-scale quantum-mechanical problems at the interface between chemistry and physics comprising both quantum chemical and model Hamiltonians. Specifically, modeling potential energy surfaces of complex electronic structures including bond breaking/formation, elucidating complex electronic structures through the picture of interacting orbitals, describing noncovalent interactions, ultra-cold trapped quantum gases, and a variety of applications in interdisciplinary quantum mechanical-based problems.

Solution method: Modular implementation of a series of unconventional (and conventional) electronic structure models based on the pCCD ansatz to solve the electronic Schrödinger equation. These include the description of both ground- and excited-states, the determination of interaction energies, and the analysis and interpretation of electronic wavefunctions. All modules are implemented in the modern Python programming language, where bottleneck operations are handled by C＋＋ code interfaced by the Pybind11 header-only library. The implemented (wavefunction) modules and modular code structure make PyBEST a very efficient alternative to existing electronic structure packages.

Additional comments including restrictions and unusual features: PyBEST features unconventional electronic structure methods (pCCD and post-pCCD methods) that are not available in any other quantum chemistry/physics software package. It also includes a general orbital entanglement and correlation module that supports both pCCD and selected post-pCCD methods. PyBEST is designed to be easy to use and code in. Due to its modularity (for instance of the tensor contraction engine), new Python modules and features can be straightforwardly imported and exploited without changing any wavefunction modules directly.

References: http://pybest.fizyka.umk.pl

中文翻译：

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Pythonic黑盒电子结构工具（PyBEST）。一个开放源代码的Python平台，用于在化学和物理之间的界面进行电子结构计算

Pythonic黑盒电子结构工具（PyBEST ）是由托伦的Nicolaus Copernicus大学开发的成熟的现代电子结构软件包。该软件包使用独特的电子结构方法，分析工具和可视化功能，在化学和物理之间的界面上为电子结构计算提供了一个高效可靠的平台。示例包括用于基态和激发态电子结构计算的（轨道优化）基于pCCD的模型，以及基于单轨道熵和轨道对互信息的量子纠缠分析框架。PyBEST主要是用Python编写的带有C ++编写的其他部分的编程语言，它们使用Pybind11（一个轻量级的仅标头库）进行接口。通过构造，PyBEST易于使用，编码以及与其他软件包的接口。此外，它的模块化特性使我们可以方便地在将来的版本中托管其他Python软件包和软件库，以增强其性能。PyBEST中可用的电子结构方法已针对半填充的一维模型哈密顿量进行了测试。维生素B ₁₂模型展示了PyBEST执行大规模电子结构计算的能力化合物。被研究的分子由190个电子和777个轨道组成，首次对其进行了pCCD内的轨道优化以及轨道纠缠和相关​​性分析。

计划摘要

程序名称： PyBEST

CPC库链接到程序文件： https : //doi.org/10.17632/xf9kb7yfwr.1

开发人员的资料库链接： https : //zenodo.org/record/3925278#.X5KAZS8Rq6s

许可条款：GNU通用公共许可3

编程语言： Python，C ＋＋

问题的性质：对具有弱相关性和强相关性的电子进行电子结构的高效且可靠的建模。化学和物理学之间的界面处的小规模和大规模量子力学问题，包括量子化学和模型哈密顿量。具体而言，对复杂的电子结构的势能面建模，包括键断裂/形成，通过相互作用的轨道图阐明复杂的电子结构，描述非共价相互作用，超冷俘获的量子气体，以及基于跨学科量子力学问题的各种应用。

解决方法：基于pCCD ansatz的一系列非常规（和常规）电子结构模型的模块化实现，以求解电子Schrödinger方程。其中包括基态和激发态的描述，相互作用能的确定以及电子波函数的分析和解释。所有模块均以现代Python编程语言实现，其中瓶颈操作由Pybind11仅标头库接口的C ++代码处理。已实现的（波函数）模块和模块化代码结构使PyBEST成为现有电子结构包的非常有效的替代品。

其他注释包括限制和异常功能： PyBEST具有非常规电子结构方法（pCCD和post-pCCD方法），而其他任何量子化学/物理学软件包均不提供这些方法。它还包括一个通用的轨道纠缠和相关​​模块，该模块支持pCCD和选定的pCCD后方法。PyBEST的设计易于使用和编写代码。由于其模块化（例如张量收缩引擎），可以直接导入和利用新的Python模块和功能，而无需直接更改任何wavefunction模块。

参考： http : //pybest.fizyka.umk.pl