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.

scholarly journals Investigations of the Hydrogen Bonds and Vibrational Spectra of Clathrate Ice XVI

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 246 ◽  
Author(s):  
Ze-Ren Wang ◽  
Xu-Liang Zhu ◽  
Lu Jiang ◽  
Kai Zhang ◽  
Hui-Wen Luo ◽  
...  
Keyword(s):  
Natural Gas ◽  
Vibrational Spectra ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Normal Modes ◽  
Inelastic Neutron ◽  
Ir Absorption ◽  
Functional Theory ◽  
Crystalline Materials ◽  
Bond Strengths

Natural gas hydrates are ice-like crystalline materials formed from natural gas and clathrate ice under high pressure and low temperature. Ice XVI, the first S-II type clathrate ice produced in the lab, was simulated by first-principles density functional theory with the CASTEP code. A 34-molecule supercell was built to mimic the hydrogen-disordered structure. The vibrational spectra were calculated as a reference for inelastic neutron scattering (INS), infrared (IR) absorption, and Raman scattering experiments. Two kinds of H-bond vibration modes corresponding to two different bond strengths were found in our previous studies. In this paper, the statistics of distribution calculated by integrating these two kinds of modes was found to match the phonon density of states (PDOS) very well. We confirmed that the two basic types of H-bonds also appeared in clathrate ice XVI. The typical normal modes were analyzed to illustrate the dynamic process of lattice vibrations.

scholarly journals Study of Anharmonicity in Zirconium Hydrides Using Inelastic Neutron Scattering and Ab-Initio Computer Modeling

Inorganics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 29
Author(s):  
Jiayong Zhang ◽  
Yongqiang Cheng ◽  
Alexander I. Kolesnikov ◽  
Jerry Bernholc ◽  
Wenchang Lu ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Excited States ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Vibrational States ◽  
Functional Theory ◽  
Hydrogen Deuterium ◽  
Zirconium Hydrides

The anharmonic phonon behavior in zirconium hydrides and deuterides, including ϵ-ZrH2, γ-ZrH, and γ-ZrD, has been investigated from aspects of inelastic neutron scattering (INS) and lattice dynamics calculations within the framework of density functional theory (DFT). The harmonic model failed to reproduce the spectral features observed in the experimental data, indicating the existence of anharmonicity in those materials and the necessity of further explanations. Here, we present a detailed study on the anharmonicity in zirconium hydrides/deuterides by exploring the 2D potential energy surface of hydrogen/deuterium atoms and solving the corresponding 2D single-particle Schrödinger equation to obtain the eigenfrequencies, which are then convoluted with the instrument resolution. The convoluted INS spectra qualitatively describe the anharmonic peaks in the experimental INS spectra and demonstrate that the anharmonicity originates from the deviations of hydrogen potentials from quadratic behavior in certain directions; the effects are apparent for the higher-order excited vibrational states, but small for the ground and first excited states.

scholarly journals DFT Simulations of the Vibrational Spectrum and Hydrogen Bonds of Ice XIV

Molecules ◽  
2018 ◽  
Vol 23 (7) ◽  
pp. 1781 ◽  
Author(s):  
Kai Zhang ◽  
Peng Zhang ◽  
Ze-Ren Wang ◽  
Xu-Liang Zhu ◽  
Ying-Bo Lu ◽  
...  
Keyword(s):  
Vibrational Spectrum ◽  
Normal Vibration ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
General Rule ◽  
Experimental Spectrum ◽  
Inelastic Neutron ◽  
Functional Theory ◽  
Ir And Raman ◽  
Normal Vibration Frequencies

It is always a difficult task to assign the peaks recorded from a vibrational spectrum. Herein, we explored a new pathway of density functional theory (DFT) simulation to present three kinds of spectra of ice XIV that can be referenced as inelastic neutron scattering (INS), infrared (IR), and Raman experimental spectrum. The INS spectrum is proportional to the phonon density of states (PDOS) while the photon scattering signals reflect the normal vibration frequencies near the Brillouin zone (BZ) center. Based on good agreements with the experimental data, we identified the relative frequency and made scientific assignments through normal vibration modes analysis. The two hydrogen bond (H-bond) peaks among the ice phases from INS were discussed and the dynamic process of the H-bond vibrations was found to be classified into two basic modes. We deduced that two H-bond modes are a general rule among the ice family and more studies are ongoing to investigate this subject.

scholarly journals Vibrational Dynamics of Crystalline 4-Phenylbenzaldehyde from INS Spectra and Periodic DFT Calculations

Molecules ◽  
2020 ◽  
Vol 25 (6) ◽  
pp. 1374
Author(s):  
Mariela M. Nolasco ◽  
Catarina F. Araujo ◽  
Pedro D. Vaz ◽  
Ana M. Amado ◽  
Paulo Ribeiro-Claro
Keyword(s):  
Dft Calculations ◽  
Single Molecule ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Torsional Mode ◽  
Functional Theory ◽  
Periodic Dft Calculations ◽  
Periodic Calculations ◽  
Unambiguous Assignment

The present work emphasizes the value of periodic density functional theory (DFT) calculations in the assessment of the vibrational spectra of molecular crystals. Periodic calculations provide a nearly one-to-one match between the calculated and observed bands in the inelastic neutron scattering (INS) spectrum of crystalline 4-phenylbenzaldehyde, thus validating their assignment and correcting previous reports based on single molecule calculations. The calculations allow the unambiguous assignment of the phenyl torsional mode at ca. 118–128 cm−1, from which a phenyl torsional barrier of ca. 4000 cm−1 is derived, and the identification of the collective mode involving the antitranslational motion of CH···O bonded pairs, a hallmark vibrational mode of systems where C-H···O contacts are an important feature.

scholarly journals Symmetry/Asymmetry of the NHN Hydrogen Bond in Protonated 1,8-Bis(dimethylamino)naphthalene

Symmetry ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1924
Author(s):  
Patrycja Piękoś ◽  
Aneta Jezierska ◽  
Jarosław J. Panek ◽  
Eugene A. Goremychkin ◽  
Alexander F. Pozharskii ◽  
...  
Keyword(s):  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Functional Theory ◽  
Protonated Forms ◽  
Motional Dynamics ◽  
Proton Dynamics ◽  
Experimental Findings ◽  
Bridge Vibrations ◽  
Theoretical Results

Experimental and theoretical results are presented based on vibrational spectra and motional dynamics of 1,8-bis(dimethylamino)naphthalene (DMAN) and its protonated forms (DMANH+ and the DMANH+ HSO4− complex). The studies of these compounds have been performed in the gas phase and solid-state. Spectroscopic investigations were carried out by infrared spectroscopy (IR), Raman, and incoherent inelastic neutron scattering (IINS) experimental methods. Density functional theory (DFT) and Car–Parrinello molecular dynamics (CPMD) methods were applied to support our experimental findings. The fundamental investigations of hydrogen bridge vibrations were accomplished on the basis of isotopic substitutions (NH → ND). Special attention was paid to the bridged proton dynamics in the DMANH+ complex, which was found to be affected by interactions with the HSO4− anion.

scholarly journals On the microscopic dynamics of the ‘Einstein solids’ AlV2Al20 and GaV2Al20, and of YV2Al20: a benchmark system for ‘rattling’ excitations

2015 ◽  
Vol 17 (38) ◽  
pp. 24837-24850 ◽  
Author(s):  
Michael Marek Koza ◽  
Hannu Mutka ◽  
Yoshihiko Okamoto ◽  
Jun-ichi Yamaura ◽  
Zenji Hiroi
Keyword(s):  
Density Functional Theory ◽  
High Resolution ◽  
Neutron Scattering ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Functional Theory ◽  
Inelastic Response ◽  
Benchmark System

The inelastic response of AV2Al20 (with A = Al, Ga and Y) was probed by high-resolution inelastic neutron scattering experiments and density functional theory (DFT) based lattice dynamics calculations (LDC).

Sign in / Sign up

Export Citation Format

Share Document