scholarly journals Ab initio paramagnetic NMR shifts via point-dipole approximation in a large magnetic-anisotropy Co(ii) complex

2018 ◽  
Vol 20 (35) ◽  
pp. 22547-22555 ◽  
Author(s):  
Jiří Mareš ◽  
Juha Vaara
Keyword(s):  
Magnetic Anisotropy ◽  
Quantum Chemical ◽  
Chemical Shifts ◽  
Computational Cost ◽  
Dipole Approximation ◽  
Paramagnetic Nmr ◽  
Point Dipole ◽  
Point Dipole Approximation ◽  
Low Computational Cost ◽  
Full Quantum

Point-dipole approximation provides accurate reproduction of full quantum-chemical results for paramagnetic NMR chemical shifts and allows extensive configurational sampling at low computational cost.

NEW FORMULATION FOR NON-EQUILIBRIUM SOLVATION: SPECTRAL SHIFTS AND CAVITY RADII OF 6-PROPANOYL-2-(N,N-DIMETHYLAMINO) NAPHTHALENE AND 4-(N,N-DIMETHYLAMINO) BENZONITRILE

2006 ◽  
Vol 05 (spec01) ◽  
pp. 355-374 ◽  
Author(s):  
YAO HUANG ◽  
XIANG-YUAN LI ◽  
KE-XIANG FU ◽  
QUAN ZHU
Keyword(s):  
Density Functional ◽  
Multipole Expansion ◽  
Dipole Approximation ◽  
Point Dipole ◽  
Functional Theory ◽  
Spectral Shifts ◽  
Point Dipole Approximation ◽  
Accessible Surface ◽  
New Formulation ◽  
Solvent Accessible Surface

In the present work, the new formulations describing spectral shifts by the authors have been introduced and employed to investigate two dye molecules, 6-propanoyl-2-(N,N-dimethylamino) naphthalene and 4-(N,N-dimethylamino) benzonitrile. From the viewpoints of the authors, the cavity radii were overestimated owing to the errors existing in the traditional models. Slightly differing from the results by other authors in the past, this work fits the cavity radii to the values of ~4.5 Å for 6-propanoyl-2-(N,N-dimethylamino) naphthalene and ~3.2 Å for 4-(N,N-dimethylamino) benzonitrile. In the fittings, both point dipole approximation and multipole expansion methods are employed. The calculations of the excited states are performed by means of the time-dependent density functional theory. Comparing the fitted cavity radii from the experimental spectra with those estimated from the molecular volumes by some well-known procedures such as COSMO and PCM, we find that the new formulations give fairly satisfactory results. By taking an atomic ion as an example, the authors argue that the Onsager radii recommended by some popular procedures are greatly exaggerated. The cavity radius derived simply from the volume encompassed by the solvent-accessible surface, without any addition of other parts, is suggested for application.

Direct Simulation of Electrorheological Suspensions

2004 ◽  
Author(s):  
Pushpendra Singh ◽  
Nadine Aubry
Keyword(s):  
Stress Tensor ◽  
Electric Fields ◽  
Electrostatic Force ◽  
Dipole Approximation ◽  
Point Dipole ◽  
Maxwell Stress ◽  
Particle Interactions ◽  
Maxwell Stress Tensor ◽  
Point Dipole Approximation ◽  
Electrorheological Suspensions

A numerical scheme based on the distributed Lagrange multiplier method (DLM) is used to study the motion of particles of a dielectric suspensions subjected to uniform and nonuniform electric fields. The Maxwell stress tensor method is used for computing electrostatic forces. In the point dipole approximation the total electrostatic force acting on a particle can be divided into two distinct contributions, one due to dielectrophoresis and the second due to particle-particle interactions. The former is zero when the applied electric field is uniform and the latter depends on the distance between the particles. In the Maxwell stress tensor approach these two contribution appear together. Simulations show that as expected the error in the point dipole approximation decreases, as the distance between the particles increases.

scholarly journals Combining Polarizable Embedding with the Frenkel Exciton Model: Applications to Absorption Spectra with Overlapping Solute-Solvent Bands

2019 ◽  
Author(s):  
Julie Stendevad ◽  
Jacob Kongsted ◽  
Casper Steinmann
Keyword(s):  
Quantum Chemical Calculations ◽  
Absorption Spectra ◽  
Quantum Chemical ◽  
Computational Cost ◽  
Frenkel Exciton ◽  
Chemical Systems ◽  
Cluster Calculations ◽  
Full Quantum ◽  
Polarizable Embedding ◽  
Chemical Description

Modeling of spectral properties of extended chemical systems, such as the case of a solute in a solvent, is often performed based on so-called hybrid models in which only part of the complete system is given a quantum chemical description. The remaining part of the system is represented by an embedding potential treating the environment either by a discrete or continuum model. In order to successfully make use of minimally sized quantum chemical regions, the<br>embedding potential should represent the environment as authentic as possible. Here, the importance of exactly such an accurate description of the embedding potential is investigated by comparing the performance of the Polarizable Embedding scheme against larger sized full quantum mechanical calculations. Our main conclusion is that as long as the solute and solvent do not overlap in their absorption spectra, the Polarizable Embedding approach shows results consistent with full quantum chemical calculations. For partly overlapping absorption spectra the Polarizable Embedding approach can furthermore successfully be expanded within a Frenkel exciton approach based on only economical monomeric quantum chemical calculations. Thus, by extending the Polarizable Embedding scheme to the exciton picture it is possible to cover computations of the whole absorption spectrum and<br>still reduce the computational cost compared to costly cluster calculations.<br>

scholarly journals Point-dipole approximation for small systems of strongly coupled radiating nanorods

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Derek W. Watson ◽  
Stewart D. Jenkins ◽  
Vassili A. Fedotov ◽  
Janne Ruostekoski
Keyword(s):  
Dipole Approximation ◽  
Point Dipole ◽  
Small Systems ◽  
Strongly Coupled ◽  
Point Dipole Approximation
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