Ab Initio Study of Vibrational Anharmonic Coupling Effects in Oligo(para-phenylenes)

2001 ◽  
Vol 708 ◽  
Author(s):  
G. Heimel ◽  
D. Somitsch ◽  
P. Knoll ◽  
E. Zojer
Keyword(s):  
Quantum Chemical ◽  
Fermi Resonance ◽  
Semiempirical Methods ◽  
Quantum Mechanical ◽  
Ab Initio Study ◽  
Coupling Effects ◽  
Anharmonic Coupling ◽  
Combination Bands ◽  
Ab Inito ◽  
Anharmonic Force

ABSTRACTIn this study we present a theoretical approach to simulate vibrational anharmonic coupling effects seen in the Raman spectra of oligo(para-phenylenes). Quantum chemical ab inito methods are applied to determine anharmonic force constants and energy corrections on the harmonic vibrational frequencies of the isolated molecules. Semiempirical methods are applied to compute Raman intensities of fundamentals and combination bands. This methodology is then used to characterize a previously unassigned Fermi resonance around 1600 cm-1. The evolution of this quantum mechanical resonance with oligomer length and planarity is compared to experimental data.

Anharmonic Coupling Revealed by the Vibrational Spectra of Solvated Protonated Methanol: Fermi Resonance, Combination Bands, and Isotope Effect

2021 ◽  
Vol 125 (9) ◽  
pp. 1910-1918
Author(s):  
Chih-Kai Lin ◽  
Qian-Rui Huang ◽  
Ying-Cheng Li ◽  
Ha-Quyen Nguyen ◽  
Jer-Lai Kuo ◽  
...  
Keyword(s):  
Isotope Effect ◽  
Vibrational Spectra ◽  
Fermi Resonance ◽  
Anharmonic Coupling ◽  
Combination Bands

Ab initio study of vibrational anharmonic coupling effects in oligo(para-phenylenes)

2002 ◽  
Vol 116 (24) ◽  
pp. 10921-10931 ◽  
Author(s):  
G. Heimel ◽  
D. Somitsch ◽  
P. Knoll ◽  
E. Zojer
Keyword(s):  
Ab Initio ◽  
Ab Initio Study ◽  
Coupling Effects ◽  
Anharmonic Coupling

The Future

1992 ◽  
Author(s):  
John A. Tossell ◽  
David J. Vaughan
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Force Fields ◽  
Structural Characteristics ◽  
Future Research ◽  
Quantum Mechanical ◽  
Bond Lengths ◽  
Hartree Fock ◽  
Qualitative Level ◽  
Dynamics Simulations

In this final chapter, an attempt is made to provide an overview of the capabilities of quantum-mechanical methods at the present time, and to highlight the needs for future development and possible future applications of these methods, particularly in areas related to mineral structures, energetics, and spectroscopy. There is also a brief account of some new areas of application, specific directions for future research, and possible developments in the perception and use of quantum-mechanical approaches. The book ends with an epilog on the overall role of “theoretical geochemistry” in the earth and environmental sciences. The local structural characteristics of minerals such as Mg2SiO4, which contain only main-group elements, are reasonably well reproduced by ab initio Hartree-Fock-Roothaan (SCF) cluster calculations at the mediumbasis- set level. Calculations incorporating configuration interaction will inevitably follow and probably lead to somewhat better agreement with experiment. The most pressing needs in this area of study are for the development of systematic procedures for cluster selection and embedding, for a greater understanding of the results at a qualitative level, and for more widespread efficient application of the quantum-chemical results currently available. In the last area, substantial progress has already been made by Lasaga and Gibbs (1987), Sanders et al. (1984), Tsuneyuki et al. (1988), and others, who have used ab initio calculations to generate theoretical force fields which can then be used in molecular-dynamics simulations. If the characteristics of the resultant force fields can be understood at a first-principles level, then it may be possible to understand details of the simulated structures at the same level. Unfortunately, as regards a greater qualitative understanding of the quantum-mechanical calculations, little progress has been made. Rather old qualitative theories describe some aspects of bond-angle variation (Tossell, 1986), but no general model to interpret variations in bond lengths has been developed within either chemistry or geochemistry beyond the model of additive atomic (Slater) or ionic (Shannon and Prewitt) radii. Indeed, global theories of bond-length variations within an ab initio framework seem to be nonexistent. Nonetheless, quantum-chemical studies have shown the presence of intriguing systematics in bond lengths (Gibbs et al., 1987), which had been already noted empirically.

scholarly journals Rational design of nanosystems for simultaneous drug delivery and photodynamic therapy by quantum mechanical modeling

Nanoscale ◽  
2019 ◽  
Vol 11 (33) ◽  
pp. 15576-15588 ◽  
Author(s):  
Moloud Kaviani ◽  
Cristiana Di Valentin
Keyword(s):  
Drug Delivery ◽  
Photodynamic Therapy ◽  
Quantum Chemical ◽  
Rational Design ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Quantum Mechanical ◽  
Mechanical Modeling

Multiscale quantum chemical study of dopamine-functionalized TiO2 nanoparticles loaded by doxorubicin with applications in drug delivery and photodynamic therapy.

On the error of approximations in quatum mechanics II. Some particular applications

1965 ◽  
Vol 257 (1081) ◽  
pp. 327-349 ◽  
Keyword(s):  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Preceding Paper ◽  
Quantum Mechanical Calculation ◽  
Quantum Mechanical ◽  
Mechanical Calculation ◽  
Matrix Calculus ◽  
General Basis ◽  
The Common

In the preceding paper (Hoffmann 1965) the author has developed the general basis of the estimation of the error in a quantum -mechanical calculation. The method based on the properties of the common trace-forming procedure in matrix calculus allowed the determination of the next approximating steps in a steepest descent process. The present paper supplies the results of applying the method to some cases usually applied in quantum -mechanical and quantum -chemical calculations.

Fermi Resonance Effects on the Vibration Modes of Hydrogen-Passivated Boron in Silicon

1989 ◽  
Vol 163 ◽  
Author(s):  
G.D. Watkins ◽  
W.B. Fowler ◽  
G.G. Deleo ◽  
M. Stavola ◽  
D.M. Kozuch ◽  
...  
Keyword(s):  
Second Harmonic ◽  
Fermi Resonance ◽  
Vibration Modes ◽  
Natural Explanation ◽  
Resonance Effects ◽  
Quantum Mechanical Treatment ◽  
Simple Quantum ◽  
Anharmonic Coupling ◽  
Quantitative Explanation ◽  
Direct Confirmation

Abstract10B - 11B isotope shifts have been reported recently for the vibrational frequencies of hydrogen (H) and its isotope deuterium (D) in the H-B complex in silicon. The D-10 B - D11 B shift was found to be anomalously large. We show that this effect finds a natural explanation in a phenomenon called “Fermi resonance”, arising from a weak anharmonic coupling between the second harmonic of the transverse B vibration and the longitudinal D vibration. We first present a simple classical explanation of the effect in terms of a “parametric oscillator”, or a child pumping a swing. We then outline a simple quantum mechanical treatment that provides a satisfactory quantitative explanation of the results. Our calculations also predict infrared absorption at the boron second harmonic frequencies. These are observed for both 10B and 11B with intensities and polarization as predicted, providing direct confirmation of the interpretation. The Pankove Si-H-B model, therefore, remains intact.

scholarly journals The IR vibrational properties of six members of the garnet family: A quantum mechanical ab initio study

2011 ◽  
Vol 96 (11-12) ◽  
pp. 1787-1798 ◽  
Author(s):  
R. Dovesi ◽  
M. De La Pierre ◽  
A. M. Ferrari ◽  
F. Pascale ◽  
L. Maschio ◽  
...  
Keyword(s):  
Ab Initio ◽  
Quantum Mechanical ◽  
Vibrational Properties ◽  
Ab Initio Study
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