Assessing the Performance of Density Functional Theory Methods on the Prediction of Low-Frequency Vibrational Spectra

2020 ◽  
Vol 41 (11) ◽  
pp. 1411-1429 ◽  
Author(s):  
Peter A. Banks ◽  
Zihui Song ◽  
Michael T. Ruggiero
Keyword(s):  
Density Functional Theory ◽  
Vibrational Spectra ◽  
Density Functional ◽  
Low Frequency ◽  
Functional Theory

scholarly journals Assessing the Performance of Density Functional Theory Methods on the Prediction of Low-Frequency Vibrational Spectra

2020 ◽  
Author(s):  
Peter Banks ◽  
Zihui Song ◽  
Michael Ruggiero
Keyword(s):  
Density Functional Theory ◽  
Vibrational Spectra ◽  
Density Functional ◽  
Low Frequency ◽  
Intermolecular Forces ◽  
State Density ◽  
Basis Set ◽  
Valuable Insight ◽  
Great Success ◽  
Functional Theory

The low-frequency (terahertz) dynamics of condensed phase materials provide valuable insight into numerous bulk phenomena. However, the assignment and interpretation of experimental results requires computational methods due to the complex mode-types that depend on weak intermolecular forces. Solid-state density functional theory has been used in this regard with great success, yet the selection of specific computational parameters, namely the chosen basis set and density functional, has a profound influence on the accuracy of predicted spectra. In this work, the role of these two parameters is investigated in a series of organic molecular crystals, in order to assess the ability of various methods to reproduce intermolecular forces, and subsequently experimental terahertz spectra. Specifically, naphthalene, oxalic acid, and thymine were chosen based on the varied intermolecular interactions present in each material. The results highlight that unconstrained geometry optimizations can be used as an initial proxy for the accuracy of interatomic forces, with errors in the calculated geometries indicative of subsequent errors in the calculated low-frequency vibrational spectra, providing a powerful metric for the validation of theoretical results. Finally, the origins of the observed shortcomings are analyzed, providing a basic framework for further studies on related materials.

scholarly journals Assessing the Performance of Density Functional Theory Methods on the Prediction of Low-Frequency Vibrational Spectra

2020 ◽  
Author(s):  
Peter Banks ◽  
Zihui Song ◽  
Michael Ruggiero
Keyword(s):  
Density Functional Theory ◽  
Vibrational Spectra ◽  
Density Functional ◽  
Low Frequency ◽  
Intermolecular Forces ◽  
State Density ◽  
Basis Set ◽  
Valuable Insight ◽  
Great Success ◽  
Functional Theory

The low-frequency (terahertz) dynamics of condensed phase materials provide valuable insight into numerous bulk phenomena. However, the assignment and interpretation of experimental results requires computational methods due to the complex mode-types that depend on weak intermolecular forces. Solid-state density functional theory has been used in this regard with great success, yet the selection of specific computational parameters, namely the chosen basis set and density functional, has a profound influence on the accuracy of predicted spectra. In this work, the role of these two parameters is investigated in a series of organic molecular crystals, in order to assess the ability of various methods to reproduce intermolecular forces, and subsequently experimental terahertz spectra. Specifically, naphthalene, oxalic acid, and thymine were chosen based on the varied intermolecular interactions present in each material. The results highlight that unconstrained geometry optimizations can be used as an initial proxy for the accuracy of interatomic forces, with errors in the calculated geometries indicative of subsequent errors in the calculated low-frequency vibrational spectra, providing a powerful metric for the validation of theoretical results. Finally, the origins of the observed shortcomings are analyzed, providing a basic framework for further studies on related materials.

Vibrational spectra of alkylamino substituted phthalocyanine compounds: Density functional theory calculations

2018 ◽  
Vol 22 (09n10) ◽  
pp. 771-776 ◽  
Author(s):  
Xin Chen ◽  
Chiming Wang ◽  
Yuxiang Chen ◽  
Dongdong Qi ◽  
Jianzhuang Jiang
Keyword(s):  
Density Functional Theory ◽  
Infrared Spectra ◽  
Vibrational Spectra ◽  
Bond Order ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Molecular Orbitals ◽  
Functional Theory ◽  
Localized Molecular Orbitals ◽  
Theoretical Investigations

The infrared spectra of tetrakis(dibutylamino) phthalocyanine and octakis(dibutylamino) compounds were studied via theoretical investigations. The results reveal deep fusion of the peripheral alkylamino moieties with the phthalocyanine chromophore in the tetrakis(dibutylamino)- but not in the octakis(dibutylamino)-phthalocyanine compounds. The successive localized molecular orbitals (LMO) and bond order analyses give support for the infrared vibrational results.

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