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1. Embedded, graph‐theoretically defined many‐body approximations for wavefunction‐in‐DFT and DFT‐in‐DFT : Applications to gas‐ and condensed‐phase ab initio molecular dynamics, and potential surfaces for quantum nuclear effects

   https://doi.org/10.1002/qua.26244  

   Ricard, Timothy C. ; Kumar, Anup ; Iyengar, Srinivasan S. ( May 2020 , International Journal of Quantum Chemistry)

   We present a graph‐theoretic approach to adaptively compute many‐body approximations in an efficient manner to perform (a) accurate post‐Hartree–Fock (HF) ab initio molecular dynamics (AIMD) at density functional theory (DFT) cost for medium‐ to large‐sized molecular clusters, (b) hybrid DFT electronic structure calculations for condensed‐phase simulations at the cost of pure density functionals, (c) reduced‐cost on‐the‐fly basis extrapolation for gas‐phase AIMD and condensed phase studies, and (d) accurate post‐HF‐level potential energy surfaces at DFT cost for quantum nuclear effects. The salient features of our approach are ONIOM‐like in that (a) the full system (cluster or condensed phase) calculation is performed at a lower level of theory (pure DFT for condensed phase or hybrid DFT for molecular systems), and (b) this approximation is improved through a correction term that captures all many‐body interactions up to any given order within a higher level of theory (hybrid DFT for condensed phase; CCSD or MP2 for cluster), combined through graph‐theoretic methods. Specifically, a region of chemical interest is coarse‐grained into a set of nodes and these nodes are then connected to form edges based on a given definition of local envelope (or threshold) of interactions. The nodes and edges together define a graph, which forms the basis for developing the many‐body expansion. The methods are demonstrated through (a) ab initio dynamics studies on protonated water clusters and polypeptide fragments, (b) potential energy surface calculations on one‐dimensional water chains such as those found in ion channels, and (c) conformational stabilization and lattice energy studies on homogeneous and heterogeneous surfaces of water with organic adsorbates using two‐dimensional periodic boundary conditions.

    

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2. Charged vacancy diffusion in chromium oxide crystal: DFT and DFT+U predictions

   https://doi.org/10.1063/1.4970882  

   Gray, Corinne ; Lei, Yinkai ; Wang, Guofeng ( December 2016 , Journal of Applied Physics)
3. H-Mediated Magnetic Interactions between Layers in a 2D Mn II -Dicyanamide Polymer: Neutron Diffraction, DFT, and Quantum Monte Carlo Calculations: H-Mediated Magnetic Interactions between Layers in a 2D Mn II -Dicyanamide Polymer: Neutron Diffraction, DFT, and Quantum Monte Carlo Calculations

   https://doi.org/10.1002/ejic.201700971  

   Gillon, Béatrice ; Hammerschmied, Albert ; Gukasov, Arsen ; Cousson, Alain ; Cauchy, Thomas ; Ruiz, Eliseo ; Schlueter, John A. ; Manson, Jamie L. ( January 2018 , European Journal of Inorganic Chemistry)
4. Atomic Scale Dynamic Process of Cu Oxidation Revealed By Correlated in situ Environmental TEM and DFT Simulations

   https://doi.org/10.1017/S1431927619008201  

   Li, Meng ; Curnan, Matthew T. ; Cresh-Sill, Michael A. ; House, Stephen D. ; Saidi, Wissam A. ; Yang, Judith C. ( August 2019 , Microscopy and Microanalysis)
5. Analyzing cases of significant nondynamic correlation with DFT using the atomic populations of effectively localized electrons

   https://doi.org/10.1007/s00214-022-02871-z  

   Lewis, Conrad ; Proynov, Emil ; Yu, Jianguo ; Kong, Jing ( March 2022 , Theoretical Chemistry Accounts)

   Quantum multireference effects are associated with degeneracies and near-degeneracies of the ground state and are critical to a variety of systems. Most approximate functionals of density functional theory (DFT) fail to properly describe such effects. A number of diagnostics have been proposed to estimate in advance the reliability of a given single-reference solution in this respect. Some of these diagnostics, however, lack size-consistency while remaining computationally expensive. In this work, we propose the DFT method of atomic populations of effectively localized electrons (APELE) as a novel diagnostic in this vein. It is compared with existing diagnostics of nondynamic correlation on select exemplary systems. The APELE method is on average in good agreement with the popular T1 index, while being size-consistent and less costly. It becomes particularly informative in cases involving bond stretching or bond breaking. The APELE method is applied next to organic diradicals like the bis-acridine dimer and the p-quinodimethane molecule which possess unusually high nonlinear optical response, and to the reaction of ethylene addition to Ni dithiolene. Our results for this reaction are consistent with the T1 diagnostics and in addition, shed some light on the degree of d-electron localization at the Ni center. 

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