All-electron LCAO calculations of the LiF crystal phonon spectrum: Influence of the basis set, the exchange-correlation functional, and the supercell size

2009 ◽  
Vol 30 (16) ◽  
pp. 2645-2655 ◽  
Author(s):  
R. A. Evarestov ◽  
M. V. Losev
Keyword(s):  
Phonon Spectrum ◽  
Basis Set ◽  
Crystal Phonon ◽  
Exchange Correlation

Evaluating Transition Metal Barrier Heights with the Latest DFT Exchange–Correlation Functionals – the MOBH35 Benchmark Dataset

2019 ◽  
Author(s):  
Mark Iron ◽  
Trevor Janes
Keyword(s):  
Transition Metal ◽  
Density Functional ◽  
Computational Cost ◽  
Basis Set ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Barrier Heights ◽  
Complete Basis Set ◽  
Complete Basis Set Limit ◽  
Hybrid Functionals

A new database of transition metal reaction barrier heights – MOBH35 – is presented. Benchmark energies (forward and reverse barriers and reaction energy) are calculated using DLPNO-CCSD(T) extrapolated to the complete basis set limit using a Weizmann1-like scheme. Using these benchmark energies, the performance of a wide selection of density functional theory (DFT) exchange–correlation functionals, including the latest from the Truhlar and Head-Gordon groups, is evaluated. It was found, using the def2-TZVPP basis set, that the ωB97M-V (MAD 1.8 kcal/mol), ωB97X-V (MAD 2.1 kcal/mol) and SCAN0 (MAD 2.1 kcal/mol) hybrid functionals are recommended. The double-hybrid functionals PWPB95 (MAD 1.6 kcal/mol) and B2K-PLYP (MAD 1.8 kcal/mol) did perform slightly better but this has to be balanced by their increased computational cost.

Computational study of polarizability anisotropies

2018 ◽  
Vol 96 (10) ◽  
pp. 934-938
Author(s):  
Delano P. Chong
Keyword(s):  
Small Molecules ◽  
Density Functional ◽  
Computational Study ◽  
Chem Phys ◽  
Basis Set ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Exchange Correlation Potential ◽  
Correlation Potential ◽  
Definition Of

The dipole polarizabilities (α) and polarizability anisotropies (Δα) of over 20 molecules are calculated to search for negative Δα. The geometry of each molecule is first optimized at the level of CCSD(T)/cc-pVQZ. Then, the α tensors are computed both with CCSD(T)/daug-cc-pVTZ in Gaussian 09 and with the exchange-correlation potential Vxc known as SAOP in the Amsterdam density functional theory program called ADF and a large basis set called QZ3P-3DIFFUSE. In addition to the popular formula of the ΔαRaman connected with Raman spectroscopy, we also present values of an alternative definition of the polarizability anisotropy ΔαKerr connected with Kerr spectroscopy, recently proposed by Kampfrath and colleagues (2018. Chem. Phys. Lett. 692: 319). On one hand, the signs of many ΔαRaman are undetermined; on the other hand, we obtain negative ΔαKerr for more than one-half of the small molecules studied. Of the 24 molecules studied, 18 have negative ΔαKerr.

scholarly journals Optical Properties of Silver-Mediated DNA from Molecular Dynamics and Time Dependent Density Functional Theory

2018 ◽  
Vol 19 (8) ◽  
pp. 2346 ◽  
Author(s):  
Esko Makkonen ◽  
Patrick Rinke ◽  
Olga Lopez-Acevedo ◽  
Xi Chen
Keyword(s):  
Molecular Dynamics ◽  
Density Functional ◽  
Time Dependent ◽  
Basis Set ◽  
Dna Nanostructures ◽  
Exchange Correlation ◽  
Hartree Fock ◽  
Spurious Peak ◽  
20 Nm ◽  
Dependent Density

We report a combined quantum mechanics/molecular mechanics (QM/MM) molecular dynamics and time-dependent density functional (TDDFT) study of metal-mediated deoxyribonucleic acid (M-DNA) nanostructures. For the Ag + -mediated guanine tetramer, we found the maug-cc-pvdz basis set to be sufficient for calculating electronic circular dichroism (ECD) spectra. Our calculations further show that the B3LYP, CAM-B3LYP, B3LYP*, and PBE exchange-correlation functionals are all able to predict negative peaks in the measured ECD spectra within a 20 nm range. However, a spurious positive peak is present in the CAM-B3LYP ECD spectra. We trace the origins of this spurious peak and find that is likely due to the sensitivity of silver atoms to the amount of Hartree–Fock exchange in the exchange-correlation functional. Our presented approach provides guidance for future computational investigations of other Ag + -mediated DNA species.

First-Principles Study of Hydrogen Storage in Fe-Ti System

2015 ◽  
Vol 365 ◽  
pp. 266-271
Author(s):  
Ahlem Khadraoui ◽  
Fatima Zohra Bentayeb
Keyword(s):  
Hydrogen Storage ◽  
First Principles ◽  
Real Space ◽  
Basis Set ◽  
Generalized Gradient ◽  
Exchange Correlation ◽  
Correlation Potential ◽  
Energy Cutoff ◽  
Bonding Properties ◽  
Pseudo Potential

In this study, a first-principles investigation of hydrogen storage in the FeTi intermetallic is carried out. The structural and electronic changes due to hydrogen insertion into the FeTi intermetallic are determined using DFT and pseudo-potential calculations through the code SIESTA (Spanish Initiative for Electronic Simulation of Thousand of Atoms). The pseudopotentials are constructed using Troullier and Martins parametrization which describes correctly the ion-electron interactions. To define the real-space grid, necessary for numerical calculations of the electron density, detailed tests were performed in order to choose the appropriate basis set, the energy cutoff and the k-grid cutoff. The exchange-correlation potential is treated with the generalized gradient approximation (GGA). Lattice data, bonding properties and the density of states provide an explanation for the role played by hydrogen in the chemical bond with the Ti and Fe constituents.

scholarly journals The Role of the CH/π Weak Interaction in the Geometrical Conformation: An Aromatic Acetamide Derivative System as an Example

2017 ◽  
Vol 56 (3) ◽  
Author(s):  
José-Zeferino Ramírez ◽  
Rubicelia Vargas ◽  
Itzia I. Padilla-Martínez ◽  
Anaid G. Flores-Huerta ◽  
Jorge Garza
Keyword(s):  
Density Functional ◽  
Basis Set ◽  
Conformational Search ◽  
Dft Methods ◽  
Theoretical Methods ◽  
Exchange Correlation ◽  
Dispersion Effects ◽  
Starting Point ◽  
Derivative System ◽  
The Many

In this work, three conformers of an aromatic amide derivative are theoretically analyzed. The theoretical methods used were based on the Kohn-Sham version of the density functional theory, considering three exchange-correlation functionals of different types: PBE, TPSS and B3LYP. The results obtained using these methods were compared to those obtained by the many-body perturbation theory to second order (MP2). All these methods where coupled with the 6-311++G(d,p) basis set. The X-ray structure was used as a starting point in the conformational search, as all the methods considered in this work had predicted that this structure would be the conformer with the highest energy, thus obtaining the first important result for this system. The second most important result discovered in this work refers to the large differences found in the predicted structures when applying DFT methods, as compared to the MP2 method. We attribute such differences to dispersion terms not included in the exchangecorrelation functionals considered; such a hypothesis is corroborated when a model system (stabilized by dispersion effects) is analyzed by applying the four theoretical methods. By incorporating dispersion effects with the exchange-correlation functional, we found they compared more favorably with the wave-function correlated method.

scholarly journals On the Efficient Evaluation of the Exchange Correlation Potential on Graphics Processing Unit Clusters

2020 ◽  
Vol 8 ◽  
Author(s):  
David B. Williams-Young ◽  
Wibe A. de Jong ◽  
Hubertus J. J. van Dam ◽  
Chao Yang
Keyword(s):  
Graphics Processing Units ◽  
High Performance ◽  
Density Functional ◽  
Materials Science ◽  
Basis Set ◽  
Theoretical Treatment ◽  
Processing Unit ◽  
Multiple Gpus ◽  
Exchange Correlation ◽  
Graphics Processing

The predominance of Kohn–Sham density functional theory (KS-DFT) for the theoretical treatment of large experimentally relevant systems in molecular chemistry and materials science relies primarily on the existence of efficient software implementations which are capable of leveraging the latest advances in modern high-performance computing (HPC). With recent trends in HPC leading toward increasing reliance on heterogeneous accelerator-based architectures such as graphics processing units (GPU), existing code bases must embrace these architectural advances to maintain the high levels of performance that have come to be expected for these methods. In this work, we purpose a three-level parallelism scheme for the distributed numerical integration of the exchange-correlation (XC) potential in the Gaussian basis set discretization of the Kohn–Sham equations on large computing clusters consisting of multiple GPUs per compute node. In addition, we purpose and demonstrate the efficacy of the use of batched kernels, including batched level-3 BLAS operations, in achieving high levels of performance on the GPU. We demonstrate the performance and scalability of the implementation of the purposed method in the NWChemEx software package by comparing to the existing scalable CPU XC integration in NWChem.

scholarly journals Comparing Study of The Stability and spectral properties vibrations for some Tellurium (IV) compounds containing cycloctadienyl group by Quantum Mechanical Calculations

2013 ◽  
Vol 10 (3) ◽  
pp. 1041-1049
Author(s):  
Baghdad Science Journal
Keyword(s):  
Density Functional ◽  
Heat Of Formation ◽  
Basis Set ◽  
Orbital Energy ◽  
Empirical Methods ◽  
Geometrical Structures ◽  
Functional Theory ◽  
Exchange Correlation ◽  
The Stability ◽  
Semi Empirical

Density Functional Theory (DFT) with B3LYP hybrid exchange-correlation functional and 3-21G basis set and semi-empirical methods (PM3) were used to calculate the energies (total energy, binding energy (Eb), molecular orbital energy (EHOMO-ELUMO), heat of formation (?Hf)) and vibrational spectra for some Tellurium (IV) compounds containing cycloctadienyl group which can use as ligands with some transition metals or essential metals of periodic table at optimized geometrical structures.

Evaluating Transition Metal Barrier Heights with the Latest DFT Exchange–Correlation Functionals – the MOBH35 Benchmark Dataset

2019 ◽  
Author(s):  
Mark Iron ◽  
Trevor Janes
Keyword(s):  
Transition Metal ◽  
Density Functional ◽  
Computational Cost ◽  
Basis Set ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Barrier Heights ◽  
Complete Basis Set ◽  
Complete Basis Set Limit ◽  
Hybrid Functionals

A new database of transition metal reaction barrier heights – MOBH35 – is presented. Benchmark energies (forward and reverse barriers and reaction energy) are calculated using DLPNO-CCSD(T) extrapolated to the complete basis set limit using a Weizmann1-like scheme. Using these benchmark energies, the performance of a wide selection of density functional theory (DFT) exchange–correlation functionals, including the latest from the Truhlar and Head-Gordon groups, is evaluated. It was found, using the def2-TZVPP basis set, that the ωB97M-V (MAD 1.8 kcal/mol), ωB97X-V (MAD 2.1 kcal/mol) and SCAN0 (MAD 2.1 kcal/mol) hybrid functionals are recommended. The double-hybrid functionals PWPB95 (MAD 1.6 kcal/mol) and B2K-PLYP (MAD 1.8 kcal/mol) did perform slightly better but this has to be balanced by their increased computational cost.

Bailyn’s exchange correlation and phonon spectrum of sodium

1965 ◽  
Vol 283 (1394) ◽  
pp. 394-402 ◽  
Keyword(s):  
Phonon Spectrum ◽  
Arbitrary Constant ◽  
The Other ◽  
Arbitrary Parameter ◽  
Matrix Elements ◽  
Phonon Interaction ◽  
Interference Factor ◽  
Exchange Correlation ◽  
Specific Heats ◽  
Electron Phonon Interaction

The phonon spectrum of sodium has been calculated by using Bailyn’s matrix elements for the electron-phonon interaction. There is satisfactory agreement with the experimental results of neutron scattering, specific heats, and elastic constants. An earlier work of the authors based on Toya’s matrix elements also gave nearly the same results. It employed an arbitrary constant α in the argument of the interference factor ( ‘g’ function). Bailyn’s expression has no arbitrary parameter and has, therefore, distinct advantages over the other.

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