Rovibrational momentum densities of diatomic molecules in the rigid rotor-harmonic oscillator approximation

1987 ◽  
Vol 142 (6) ◽  
pp. 455-462 ◽  
Author(s):  
Brian A. Pettitt ◽  
Werner Danchura
Keyword(s):  
Harmonic Oscillator ◽  
Diatomic Molecules ◽  
Rigid Rotor ◽  
Harmonic Oscillator Approximation

scholarly journals On the Complementarity of the Harmonic Oscillator Model and the Classical Wigner–Kirkwood Corrected Partition Functions of Diatomic Molecules

Entropy ◽  
2020 ◽  
Vol 22 (8) ◽  
pp. 853
Author(s):  
Marcin Buchowiecki
Keyword(s):  
Phase Space ◽  
Partition Function ◽  
Harmonic Oscillator ◽  
High Temperatures ◽  
Low Temperatures ◽  
Diatomic Molecules ◽  
Partition Functions ◽  
Harmonic Oscillator Model ◽  
Harmonic Oscillator Approximation ◽  
Classical Partition Function

The vibrational and rovibrational partition functions of diatomic molecules are considered in the regime of intermediate temperatures. The low temperatures are those at which the harmonic oscillator approximation is appropriate, and the high temperatures are those at which classical partition function (with Wigner–Kirkwood correction) is applicable. The complementarity of the harmonic oscillator and classical integration over the phase space approaches is investigated for the CO and H2+ molecules showing that those two approaches are complementary in the sense that they smoothly overlap.

scholarly journals GoodVibes: automated thermochemistry for heterogeneous computational chemistry data

F1000Research ◽  
2020 ◽  
Vol 9 ◽  
pp. 291 ◽  
Author(s):  
Guilian Luchini ◽  
Juan V. Alegre-Requena ◽  
Ignacio Funes-Ardoiz ◽  
Robert S. Paton
Keyword(s):  
Harmonic Oscillator ◽  
Computational Chemistry ◽  
Open Source ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Basis Set ◽  
Partition Functions ◽  
Rigid Rotor ◽  
Computational Data ◽  
Publication Quality

GoodVibes is an open-source Python toolkit for processing the results of quantum chemical calculations. Thermochemical data are not simply parsed, but evaluated by evaluation of translational, rotational, vibrational and electronic partition functions. Changes in concentration, pressure, and temperature can be applied, and deficiencies in the rigid rotor harmonic oscillator treatment can be corrected. Vibrational scaling factors can also be applied by automatic detection of the level of theory and basis set. Absolute and relative thermochemical values are output to text and graphical plots in seconds. GoodVibes provides a transparent and reproducible way to process raw computational data into publication-quality tables and figures without the use of spreadsheets.

scholarly journals Shermo: A General Code for Calculating Molecular Thermochemistry Properties

2020 ◽  
Author(s):  
Tian Lu ◽  
qinxue chen
Keyword(s):  
Quantum Chemistry ◽  
Harmonic Oscillator ◽  
Thermodynamic Data ◽  
Thermodynamic Quantities ◽  
Rigid Rotor ◽  
Low Frequencies ◽  
Frequency Scale ◽  
Scale Factors ◽  
Temperature And Pressure ◽  
Output Information

Calculation of molecular thermodynamic quantities is one of the most frequently involved task in daily quantum chemistry studies. In this article, we present a general, stand-alone, powerful and flexible code named Shermo for calculating various common thermochemistry data. This code is compatible with Gaussian, ORCA, GAMESS-US and NWChem and has many unique advantages: the output information is very easy to comprehend; thermodynamic quantities can be fully decomposed to contributions of various sources; temperature and pressure can be conveniently scanned; two quasi-rigid-rotor harmonic oscillator (quasi-RRHO) models are supported to properly deal with low frequencies; different frequency scale factors can be simultaneously specified for calculating different thermodynamic quantities; conformation weighted thermodynamic data can be directly evaluated; the code can be easily run and embedded into shell script. We hope the Shermo program will bring great convenience to quantum chemists. This code can be freely obtained at http://sobereva.com/soft/shermo.

The Influence of Molecular Vibration on Brayton-Cycle Performance

1962 ◽  
Vol 29 (2) ◽  
pp. 396-398
Author(s):  
T. A. Jacobs ◽  
J. R. Lloyd
Keyword(s):  
Harmonic Oscillator ◽  
Cycle Performance ◽  
Molecular Vibration ◽  
Brayton Cycle ◽  
Harmonic Oscillator Approximation

By means of the harmonic-oscillator approximation, the influence of molecular vibration on Brayton-cycle performance is demonstrated.

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