EDF2: A Density Functional for Predicting Molecular Vibrational Frequencies

2004 ◽  
Vol 57 (4) ◽  
pp. 365 ◽  
Author(s):  
Ching Yeh Lin ◽  
Michael W. George ◽  
Peter M. W. Gill
Keyword(s):  
Vibrational Spectra ◽  
Density Functional ◽  
Functional Model ◽  
Harmonic Approximation ◽  
Vibrational Frequencies ◽  
Computational Approach ◽  
Numerical Results ◽  
Harmonic Frequencies ◽  
Anharmonic Frequencies ◽  
Computationally Expensive

The majority of calculations of molecular vibrational spectra are based on the harmonic approximation but are compared (usually after empirical scaling) with experimental anharmonic frequencies. Any agreement that is observed in such cases must be attributable to fortuitous cancellation of errors and it would certainly be preferable to develop a more rigorous computational approach. In this paper, we introduce a new density functional model (EDF2) that is explicitly designed to yield accurate harmonic frequencies, and we present numerical results for a wide variety of molecules whose experimental harmonic frequencies are known. The EDF2 model is found to be significantly more accurate than other DFT models and competitive with the computationally expensive CCSD(T) method.

A DFT Analysis of the Molecular Structures and Vibrational Spectra of Diphenylsulfone and 4,4'-Sulfonyldianiline (Dapsone)

2011 ◽  
Vol 66 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Wolfgang Förner ◽  
Hassan M. Badawi
Keyword(s):  
Vibrational Spectra ◽  
Density Functional ◽  
Parent Compound ◽  
Harmonic Approximation ◽  
Molecular Structures ◽  
Spectral Lines ◽  
Basis Set ◽  
Minor Role ◽  
Parent Molecule ◽  
Chemical Difference

We have performed density functional calculations with the B3LYP functional and a 6-311G** basis set to obtain the vibrational spectra in harmonic approximation of the anti-leprosy drug Dapsone and the parent compound diphenylsulfone. Although the chemical difference between the two molecules is not that pronounced (Dapsone has amino groups in the para positions in the phenyl rings), Dapsone is an active drug, while to our knowledge diphenylsulfone shows no medical activity. We compared the theoretical results to experimental vibrational spectra found in the literature. With the help of the program GAUSSVIEW we were able to assign the experimentally found spectral lines to specific atomic motions. The remarkable difference between the two molecules, regarding their structural behavior, is that the drug Dapsone has a more flexible structure of the phenyl ring than the parent molecule has. This might contribute to a greater ability of the drug to fit into receptor sites in a cell membrane although one has to be well aware that this plays most propably only a minor role in the drug activity of Dapsone

Vibrational frequencies of the diced and decorated honeycomb lattices

2019 ◽  
Vol 33 (08) ◽  
pp. 1950058 ◽  
Author(s):  
M. Q. Owaidat
Keyword(s):  
Lattice Dynamics ◽  
Vibrational Mode ◽  
Harmonic Approximation ◽  
Vibrational Frequencies ◽  
Numerical Results ◽  
Two Dimensional ◽  
Classical Lattice

In this paper, the classical lattice dynamics for the two-dimensional diced and decorated honeycomb lattices in the harmonic approximation is studied. The numerical results for the vibrational mode frequencies are presented.

scholarly journals Quantum Mechanical Modeling of the Vibrational Spectra of Minerals with a Focus on Clays

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 141 ◽  
Author(s):  
James Kubicki ◽  
Heath Watts
Keyword(s):  
Vibrational Spectra ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Isotopic Fractionation ◽  
Inelastic Neutron ◽  
Vibrational Frequencies ◽  
Quantum Mechanical ◽  
Dft Methods ◽  
Additional Information ◽  
Starting Point

We present an overview of how to use quantum mechanical calculations to predict vibrational frequencies of molecules and materials such as clays and silicates. Other methods of estimating vibrational frequencies are mentioned, such as classical molecular dynamics simulations; references are given for additional information on these approaches. Herein, we discuss basic vibrational theory, calculating Raman and infrared intensities, steps for creating realistic models, and applications to spectroscopy, thermodynamics, and isotopic fractionation. There are a wide variety of programs and methods that can be employed to model vibrational spectra, but this work focuses on hybrid density functional theory (DFT) approaches. Many of the principles are the same when used in other programs and DFT methods, so a novice can benefit from simple examples that illustrate key points to consider when modeling vibrational spectra. Other methods and programs are listed to give the beginner a starting point for exploring and choosing which approach will be best for a given problem. The modeler should also be aware of the numerous analytical methods available for obtaining information on vibrations of atoms in molecules and materials. In addition to traditional infrared and Raman spectroscopy, sum-frequency generation (SFG) and inelastic neutron scattering (INS) are also excellent techniques for obtaining vibrational frequency information in certain circumstances.

Accurate vibrational spectra of large molecules by density functional computations beyond the harmonic approximation: the case of uracil and 2-thiouracil

2004 ◽  
Vol 388 (4-6) ◽  
pp. 279-283 ◽  
Author(s):  
Vincenzo Barone ◽  
Gaetano Festa ◽  
Andrea Grandi ◽  
Nadia Rega ◽  
Nico Sanna
Keyword(s):  
Vibrational Spectra ◽  
Density Functional ◽  
Harmonic Approximation ◽  
Large Molecules ◽  
Density Functional Computations
Sign in / Sign up

Export Citation Format

Share Document