scholarly journals Linear-Scaling Open-Shell MP2 Approach: Algorithm, Benchmarks, and Large-Scale Applications

2021 ◽  
Author(s):  
P. Bernát Szabó ◽  
József Csóka ◽  
Mihály Kállay ◽  
Péter R. Nagy
Keyword(s):  
Large Scale ◽  
Open Shell ◽  
Linear Scaling

scholarly journals The Effect of Hartree-Fock Exchange on Scaling Relations and Reaction Energetics for C–H Activation Catalysts

2021 ◽  
Author(s):  
Vyshnavi Vennelakanti ◽  
Aditya Nandy ◽  
Heather Kulik
Keyword(s):  
Spin State ◽  
Density Functional ◽  
Large Scale ◽  
Predictive Power ◽  
Minimum Energy ◽  
Poor Performance ◽  
Closed Shell ◽  
Open Shell ◽  
Methanol Conversion ◽  
Hartree Fock

<p>High-throughput computational catalyst studies are typically carried out using density functional theory (DFT) with a single, approximate exchange-correlation functional. In open shell transition metal complexes (TMCs) that are promising for challenging reactions (e.g., C–H activation), the predictive power of DFT has been challenged, and properties are known to be strongly dependent on the admixture of Hartree-Fock (HF) exchange. We carry out a large-scale study of the effect of HF exchange on the predicted catalytic properties of over 1,200 mid-row (i.e., Cr, Mn, Fe, Co) 3<i>d </i>TMCs for direct methane-to-methanol conversion. Reaction energetic sensitivities across this set depend both on the catalytic rearrangement and ligand chemistry of the catalyst. These differences in sensitivities change both the absolute energetics predicted for a catalyst and its relative performance. Previous observations of the poor performance of global linear free energy relationships (LFERs) hold with both semi-local DFT widely employed in heterogeneous catalysis and hybrid DFT. Narrower metal/oxidation/spin-state specific LFERs perform better and are less sensitive to HF exchange than absolute reaction energetics, except in the case of some intermediate/high-spin states. Importantly, the interplay between spin-state dependent reaction energetics and exchange effects on spin-state ordering means that the choice of DFT functional strongly influences whether the minimum energy pathway is spin-conserved. Despite these caveats, LFERs involving catalysts that can be expected to have closed shell intermediates and low-spin ground states retain significant predictive power.</p>

scholarly journals A Practical Approach to Large Scale Electronic Structure Calculations in Electrolyte Solutions via Continuum-Embedded Linear-Scaling DFT

2020 ◽  
Author(s):  
Jacek Dziedzic ◽  
Arihant Bhandari ◽  
Lucian Anton ◽  
Chao Peng ◽  
James Womack ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Density Functional ◽  
Large Scale ◽  
Ethylene Carbonate ◽  
Electrostatic Energy ◽  
Open Boundary ◽  
Linear Scaling ◽  
Open Boundary Conditions ◽  
Electrostatic Problem ◽  
Poisson Boltzmann

We present the implementation of a hybrid continuum-atomistic model for including the effects of surrounding electrolyte in large-scale density functional theory (DFT) calculations within the ONETEP linear-scaling DFT code, which allows the simulation of large complex systems such as electrochemical interfaces. The model represents the electrolyte ions as a scalar field and the solvent as a polarisable dielectric continuum, both surrounding the quantum solute. The overall energy expression is a grand canonical functional incorporating the electron kinetic and exchange correlation energies, the total electrostatic energy, entropy and chemical potentials of surrounding electrolyte, osmotic pressure, and the effects of cavitation, dispersion and repulsion. The DFT calculation is performed fully self-consistently in the electrolyte model, allowing the quantum mechanical system and the surrounding continuum environment to interact and mutually polarize. A bespoke parallel Poisson-Boltzmann solver library, DL_MG, deals with the electrostatic problem, solving a generalized Poisson-Boltzmann equation. Our model supports open boundary conditions, which allows the treatment of molecules, entire biomolecules or larger nanoparticle assemblies in electrolyte. We have also implemented the model for periodic boundary conditions, allowing the treatment of extended systems such as electrode surfaces in contact with electrolyte. A key feature of the model is the use of solute-size and solvation-shell-aware accessibility functions that prevent the unphysical accumulation of electrolyte charge near the quantum solute boundary. The model has a small number of parameters: here we demonstrate their calibration against experimental mean activity coefficients. We also present an exemplar simulation of a 1634-atom model of the interface between a graphite anode and LiPF<sub>6</sub> electrolyte in ethylene carbonate solvent. We compare the cases where Li atoms are intercalated at opposite edges of the graphite slab and in solution, demonstrating a potential application of the model in simulations of fundamental processes in Li-ion batteries.

scholarly journals Linear-scaling density functional simulations of the effect of crystallographic structure on the electronic and optical properties of fullerene solvates

2017 ◽  
Vol 19 (7) ◽  
pp. 5617-5628 ◽  
Author(s):  
Hong-Tao Xue ◽  
Gabriele Boschetto ◽  
Michal Krompiec ◽  
Graham E. Morse ◽  
Fu-Ling Tang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Dft Calculations ◽  
Density Functional ◽  
Large Scale ◽  
Crystallographic Structure ◽  
Linear Scaling ◽  
Optical Absorption Spectra ◽  
Novel Structure ◽  
Structural And Electronic Properties

Large-scale DFT calculations of fullerene solvates including one novel structure probe, the structural and electronic properties and optical absorption spectra.

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