scholarly journals Large-scale atomistic simulations of nanostructured materials based on divide-and-conquer density functional theory

2011 ◽  
Vol 196 (1) ◽  
pp. 53-63 ◽  
Author(s):  
F. Shimojo ◽  
S. Ohmura ◽  
A. Nakano ◽  
R. K. Kalia ◽  
P. Vashishta
Keyword(s):  
Density Functional Theory ◽  
Nanostructured Materials ◽  
Density Functional ◽  
Large Scale ◽  
Divide And Conquer ◽  
Atomistic Simulations ◽  
Functional Theory

Benchmark of Simplified Time-Dependent Density Functional Theory for UV-Vis Spectral Properties of Porphyrinoids

2019 ◽  
Author(s):  
Kamal Batra ◽  
Stefan Zahn ◽  
Thomas Heine
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Absolute Error ◽  
Time Dependent ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
Framework Materials ◽  
Dependent Density

<p>We thoroughly benchmark time-dependent density- functional theory for the predictive calculation of UV/Vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, we compare the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density-functional theory, including the simplified Tamm-Dancoff approximation. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm-Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ~0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ~0.04 eV). </p>

scholarly journals Tensor-structured algorithm for reduced-order scaling large-scale Kohn–Sham density functional theory calculations

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Chih-Chuen Lin ◽  
Phani Motamarri ◽  
Vikram Gavini
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Density Functional Theory Calculations ◽  
System Size ◽  
Real Space ◽  
Functional Theory ◽  
Reduced Order ◽  
Separable Approximation ◽  
Tensor Basis

AbstractWe present a tensor-structured algorithm for efficient large-scale density functional theory (DFT) calculations by constructing a Tucker tensor basis that is adapted to the Kohn–Sham Hamiltonian and localized in real-space. The proposed approach uses an additive separable approximation to the Kohn–Sham Hamiltonian and an L1 localization technique to generate the 1-D localized functions that constitute the Tucker tensor basis. Numerical results show that the resulting Tucker tensor basis exhibits exponential convergence in the ground-state energy with increasing Tucker rank. Further, the proposed tensor-structured algorithm demonstrated sub-quadratic scaling with system-size for both systems with and without a gap, and involving many thousands of atoms. This reduced-order scaling has also resulted in the proposed approach outperforming plane-wave DFT implementation for systems beyond 2000 electrons.

Plasmonic resonances of nanoparticles from large-scale quantum mechanical simulations

2017 ◽  
Vol 31 (24) ◽  
pp. 1740003 ◽  
Author(s):  
Xu Zhang ◽  
Hongping Xiang ◽  
Mingliang Zhang ◽  
Gang Lu
Keyword(s):  
Density Functional Theory ◽  
Metallic Nanoparticles ◽  
Density Functional ◽  
Large Scale ◽  
Incident Light ◽  
Time Dependent ◽  
Coherent Motion ◽  
Quantum Mechanical ◽  
Functional Theory ◽  
Conduction Electrons

Plasmonic resonance of metallic nanoparticles results from coherent motion of its conduction electrons, driven by incident light. For the nanoparticles less than 10 nm in diameter, localized surface plasmonic resonances become sensitive to the quantum nature of the conduction electrons. Unfortunately, quantum mechanical simulations based on time-dependent Kohn–Sham density functional theory are computationally too expensive to tackle metal particles larger than 2 nm. Herein, we introduce the recently developed time-dependent orbital-free density functional theory (TD-OFDFT) approach which enables large-scale quantum mechanical simulations of plasmonic responses of metallic nanostructures. Using TD-OFDFT, we have performed quantum mechanical simulations to understand size-dependent plasmonic response of Na nanoparticles and plasmonic responses in Na nanoparticle dimers and trimers. An outlook of future development of the TD-OFDFT method is also presented.

Mass Spectrometry of Cyclopentadienylideneketene: Differentiation of Isomeric Ion Structures by Means of Ion/Molecule Reactions

2012 ◽  
Vol 65 (12) ◽  
pp. 1655 ◽  
Author(s):  
Pascal Gerbaux ◽  
Curt Wentrup
Keyword(s):  
Mass Spectrometry ◽  
Density Functional Theory ◽  
Density Functional ◽  
Large Scale ◽  
Density Functional Theory Calculations ◽  
Molecular Ions ◽  
Functional Theory ◽  
Clear Cut ◽  
Ion Molecule Reactions ◽  
Hybrid Mass Spectrometer

The nature of the m/z 104 ions formed by loss of CO2 or Ph-O-NCO from the molecular ions of phthalic anhydride, N-phenoxyphthalimide, and N-phenoxyisophthalimide was investigated by means of ion/molecule reactions with acetone. This allows a clear-cut differentiation of the so-obtained ions from the isomeric molecular ions of cyclopentadienylideneketene. The different intrinsic chemical reactivities of ionized cyclopentadienylideneketene and its distonoid isomer towards neutral acetone were investigated on a large-scale hybrid mass spectrometer and confirmed by density functional theory calculations.

scholarly journals Large-Scale Density Functional Theory Transition State Searching in Enzymes

2014 ◽  
Vol 5 (21) ◽  
pp. 3614-3619 ◽  
Author(s):  
Greg Lever ◽  
Daniel J. Cole ◽  
Richard Lonsdale ◽  
Kara E. Ranaghan ◽  
David J. Wales ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Density Functional ◽  
Large Scale ◽  
Functional Theory
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