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arXiv · 1709.10315

CERES: An ab initio code dedicated to the calculation of the electronic structure and magnetic properties of lanthanide complexes

Simone Calvello·Matteo Piccardo·Shashank V. Rao·Alessandro Soncini
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Abstract

We have developed and implemented a new ab initio code, CERES (Computational Emulator of Rare Earth Systems), completely written in C++11, which is dedicated to the efficient calculation of the electronic structure and magnetic properties of the crystal field states arising from the splitting of the ground state spin-orbit multiplet in lanthanide complexes. The new code gains efficiency via an optimised implementation of a direct configurational averaged Hartree-Fock (CAHF) algorithm for the determination of $4f$ quasi-atomic active orbitals common to all multi-electron spin manifolds contributing to the ground spin-orbit multiplet of the lanthanide ion. The new CAHF implementation is based on quasi-Newton convergence acceleration techniques coupled to an efficient library for the direct evaluation of molecular integrals, and problem-specific density matrix guess strategies. After describing the main features of the new code, we compare its efficiency with the current state--of--the--art ab initio strategy to determine crystal field levels and properties, and show that our methodology, as implemented in CERES, represents a more time-efficient computational strategy for the evaluation of the magnetic properties of lanthanide complexes, also allowing a full representation of non-perturbative spin-orbit coupling effects.

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Simone Calvello, Matteo Piccardo, Shashank V. Rao, Alessandro Soncini. 2017-09-29. CERES: An ab initio code dedicated to the calculation of the electronic structure and magnetic properties of lanthanide complexes. https://arxiv.org/abs/1709.10315

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