Time‐dependent Hartree–Fock second‐order molecular properties with a moderately sized basis set. II. Dispersion coefficients

1991 ◽  
Vol 94 (2) ◽  
pp. 1295-1305 ◽  
Author(s):  
Mark A. Spackman
Keyword(s):  
Second Order ◽  
Molecular Properties ◽  
Time Dependent ◽  
Basis Set ◽  
Dispersion Coefficients ◽  
Hartree Fock

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.

Protonation Effect on C-N Bond Length of Alkylamines Studied by Molecular Orbital Calculations

2000 ◽  
Vol 55 (9-10) ◽  
pp. 769-771 ◽  
Keyword(s):  
Density Functional Theory ◽  
Bond Length ◽  
Molecular Orbital ◽  
Density Functional ◽  
Second Order ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Functional Theory ◽  
Hartree Fock ◽  
Protonation Effect

Abstract Molecular orbital calculations were performed for the six saturated alkylamines (CH3NH2 , (CH3)2 NH, (CH 3)3 N, CH 3CH2NH2 , (CH3)2 CHNH2 , (CH3)3 CNH2), their protonated cations (CH3NH3 + , (CH3)2NH2 + , (CH3)3NH + , CH3CH2NH3 + , (CH3)2CHNH3 + , (CH3)3CNH3+), and (CH3)4 N + using the Hartree-Fock, second-order M0ller-Plesset, and density functional theory methods with the 6-311+G(d,p) basis set. Protonation lengthens the C-N bonds of the amines by 0.05 -0.08 Å and shortens the C-C bonds of CH3CH2NH2, (CH3)2CHNH2 , and (CH3)3CNH2 by ca. 0.01 Å.

Recent Advances in ab initio time—dependent Hartree-Fock theory and their applications to predict nonlinear optical properties of semiconductor nanoclusters

1999 ◽  
Vol 579 ◽  
Author(s):  
Shashi P. Karna ◽  
Prakashan P. Korambath
Keyword(s):  
Ab Initio ◽  
Nonlinear Optical ◽  
Time Dependent ◽  
Basis Set ◽  
Order Effects ◽  
Hartree Fock ◽  
Nlo Property ◽  
Nlo Materials ◽  
A Charge ◽  
Hf Calculations

ABSTRACTRecent advancements in ab initio time-dependent Hartree-Fock (TDHF) theory have made it a technique of choice for modeling nanoscale nonlinear optical (NLO) materials from first-principles. We have used this method to study structure-NLO property relationships of GaN, GaP and GaAs clusters. The geometry of the clusters used in the study was optimized by ab initio Hartree Fock (HF) calculations with the use of even tempered Gaussian (ETG) basis set. The clusters used in this study are of the type Gam Xn (M = 1,3,4,7 and n = 1,3,4,7) where X=N, P, and As. The GamXn clusters are in a charge neutral (q = 0) state for m = n and in appropriately charged state for m ∦ n. The magnitude of the calculated (hyper)polarizabilities appears to strongly depend on the composition of the cluster. For the same composition of heteroatoms, the hyperpolarizability depends on the size as well as the geometry of the cluster. The cluster size-dependence of calculated (hyper)polarizabilities is more pronounced for the first-hyperpolarizability. β than for the polarizability, α The calculated β(–ωμ,ωl,ω2) corresponding to various second order effects shows the following trend β(–2ω; ω,ω) > β(–ω; 0, ω) >β(0;0,0).

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