PyFLOSIC: Python-based Fermi–Löwdin orbital self-interaction correction

Abstract

We present pyflosic, an open-source, general-purpose python implementation of the Fermi–Löwdin orbital self-interaction correction (FLO-SIC), which is based on the python simulation of chemistry framework (pyscf) electronic structure and quantum chemistry code. Thanks to pyscf, pyflosic can be used with any kind of Gaussian-type basis set, various kinds of radial and angular quadrature grids, and all exchange-correlation functionals within the local density approximation, generalized-gradient approximation (GGA), and meta-GGA provided in the libxc and xcfun libraries. A central aspect of FLO-SIC is the Fermi-orbital descriptors, which are used to estimate the self-interaction correction. Importantly, they can be initialized automatically within pyflosic; they can also be optimized within pyflosic with an interface to the atomic simulation environment, a python library that provides a variety of powerful gradient-based algorithms for geometry optimization. Although pyflosic has already facilitated applications of FLO-SIC to chemical studies, it offers an excellent starting point for further developments in FLO-SIC approaches, thanks to its use of a high-level programming language and pronounced modularity.

Implementation of Perdew–Zunger self-interaction correction in real space using Fermi–Löwdin orbitals

“…The FLOSIC method has been implemented in Gaussian-orbital-based packages and has been successfully applied to study a wide array of electronic properties. 15,16,44,[57][58][59][60][62][63][64][65][66][67][76][77][78][79] In this work, we present a formulation and implementation of the FLOSIC method in real space. The real-space formulation enables rigorous, systematic convergence for all atomic species and configurations as well as large-scale parallelism to reach larger length and time scales than previously accessible at this level of theory.…”

“…110 The default basis set 111 is shown to give comparable results to the cc-pVQZ basis set. 44 Calculations were also performed using the PyFLOSIC code 112 , a pySCF 113 based code, to produce benchmark calculations for comparison as it allows using basis sets with higher angular momentum functions. Non-self-consistent one-shot (OS) calculations were performed by calculating SIC energies at the end of a standard DFT calculation using the converged Kohn-Sham orbitals.…”

Testing Self‐Interaction Correction for Molecules in Solution

“…It is generally accepted [25][26][27][28][29] that E SIC , and thus E PZ , assumes lower values if localized orbitals are used in the construction of n σ i ðxÞ, compared with the use of delocalized orbitals. The FLO-SIC approach to Equation (6) has been the subject of extensive study in recent years, and it is discussed in detail in, e.g., Section II of Schwalbe et al, [30] to which we point for further information. FLO-SIC is defined by constraining the localized orbitals used for the SIC to be Fermi-Löwdin orbitals (FLOs).…”

Free and Open Source Software for Computational Chemistry Education

“…Being able to use software written by other authors to accomplish certain tasks eliminates the need to "reinvent the wheel" and thereby results in faster scientific development. 24 This phenomenon has traditionally been the main enticement of contributing to closed-source or "open teamware" 25 packages, as access to their source code partly eliminates the need to start from scratch, as algorithms implemented by the other contributors can be leveraged to develop new computational models.…”