extended systems
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Author(s):  
Elisabeth Keller ◽  
Theodoros Tsatsoulis ◽  
Karsten Reuter ◽  
Johannes Theo Margraf

2021 ◽  
Author(s):  
Elisabeth Keller ◽  
Theodoros Tsatsoulis ◽  
Karsten Reuter ◽  
Johannes T. Margraf

While many-body wavefunction theory has long been established as a powerful framework for highly accurate molecular quantum chemistry, these methods have only fairly recently been applied to extended systems in a significant scale. This is due to the high computational cost of such calculations, requiring efficient implementations and ample computing resources. To further aggravate this, second-order Møller-Plesset perturbation theory (MP2) (the most cost effective wavefuntion method) is known to diverge or fail for some prototypical condensed matter systems like the homogeneous electron gas (HEG). In this paper, we explore how the issues of MP2 for metallic and strongly correlated systems can be ameliorated through regularization. To this end, two regularized second-order methods (including a new, size-extensive Brillioun-Wigner approach) are applied to the HEG, the one-dimensional Hubbard model and the graphene-water interaction energy. We find that regularization consistently leads to improvements over the MP2 baseline and that different regularizers are appropriate for metallic and strongly correlated systems, respectively.


2021 ◽  
Vol 104 (7) ◽  
Author(s):  
Mizuki Tani ◽  
Tomohito Otobe ◽  
Yasushi Shinohara ◽  
Kenichi L. Ishikawa

2021 ◽  
Vol 94 (7) ◽  
Author(s):  
Jörg Behler ◽  
Gábor Csányi

Abstract In the past two and a half decades machine learning potentials have evolved from a special purpose solution to a broadly applicable tool for large-scale atomistic simulations. By combining the efficiency of empirical potentials and force fields with an accuracy close to first-principles calculations they now enable computer simulations of a wide range of molecules and materials. In this perspective, we summarize the present status of these new types of models for extended systems, which are increasingly used for materials modelling. There are several approaches, but they all have in common that they exploit the locality of atomic properties in some form. Long-range interactions, most prominently electrostatic interactions, can also be included even for systems in which non-local charge transfer leads to an electronic structure that depends globally on all atomic positions. Remaining challenges and limitations of current approaches are discussed. Graphic Abstract


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