scholarly journals Структура и динамика решетки тетрагональных германатов R-=SUB=-2-=/SUB=-Ge-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- (R=Tb-Lu, Y): ab initio расчет

2021 ◽  
Vol 63 (6) ◽  
pp. 797
Author(s):  
В.С. Рюмшин ◽  
В.А. Чернышев
Keyword(s):  
Ab Initio ◽  
Raman Spectra ◽  
Ab Initio Calculation ◽  
Density Functional ◽  
Ir And Raman Spectra ◽  
Displacement Vectors ◽  
Raman Modes ◽  
Degree Of Participation ◽  
First Time ◽  
Ir And Raman

Within the framework of density functional theory, an ab initio calculation was carried out to study the crystal structure, phonon spectrum and elastic constants of a series of rare-earth germanates, including yttrium germanate R2Ge2O7 (R = Tb-Lu, Y) with tetragonal structure. The frequencies and types of fundamental vibrations as well as the intensities of the IR and Raman modes were determined. The degree of participation of ions in each mode was determined from the analysis of the displacement vectors obtained from the ab initio calculation. The calculations were performed for the first time. The corresponding experimental data for the entire series, with the exception of the IR and Raman spectra of yttrium germanate, are absent. The calculations made it possible to interpret and supplement available in the scientific articles results of measurements of the IR and Raman spectra of yttrium germanate Y2Ge2O7.

scholarly journals Фононный спектр и упругие свойства Y-=SUB=-2-=/SUB=-Sn-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=-

2021 ◽  
Vol 129 (8) ◽  
pp. 1027
Author(s):  
В.А. Чернышев ◽  
К.И. Глухов ◽  
П.А. Агзамова
Keyword(s):  
Ab Initio ◽  
Elastic Constants ◽  
Phonon Modes ◽  
Displacement Vectors ◽  
Raman Modes ◽  
Impurity Centers ◽  
Ab Initio Approach ◽  
Degree Of Participation ◽  
Impurity Ion ◽  
Ir And Raman

In the framework of a unified ab initio approach, the phonon spectrum of yttrium stannate Y2Sn2O7 was calculated, the frequencies and types of IR and Raman modes were determined. From an analysis of the displacement vectors obtained in ab initio calculations, the degree of participation of ions in phonon modes is determined. The elastic constants and hardness of Y2Sn2O7 are calculated. The distance "impurity ion-ligand" in impurity centers Y2Sn2O7: Yb3 +, Y2Sn2O7: Eu3 +, Lu2Sn2O7: Yb3 +, Nd2Sn2O7: Gd3 +, Nd2Sn2O7: Tb3 + is calculated.

scholarly journals Структура и динамика решетки редкоземельных станнатов R-=SUB=-2-=/SUB=-Sn-=SUB=-2-=/SUB=-O-=SUB=-7-=/SUB=- (R=La-Lu): ab initio расчет

2021 ◽  
Vol 63 (7) ◽  
pp. 952
Author(s):  
В.А. Чернышев
Keyword(s):  
Rare Earth ◽  
Ab Initio ◽  
Phonon Modes ◽  
Rare Earth Ion ◽  
Third Order ◽  
Displacement Vectors ◽  
Degree Of Participation ◽  
Murnaghan Equation ◽  
First Time ◽  
Ir And Raman

The ab initio study of the structure and dynamics of the lattice, as well as the elastic properties of a row of rare-earth stannates R2Sn2O7 (R = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) has been carried out for first time. The IR and Raman spectra were calculated, the types of phonon modes were determined. The degree of participation of ions in phonon modes is determined. Modes with the absolute or predominant participation of oxygen in the 48f position, characterized by a shift x, were determined from an analysis of the displacement vectors obtained from the ab initio calculations. The elastic constants and the hardness HV have been calculated. The effect of hydrostatic compression on the crystal structure is investigated. It is shown that the degree of distortion of the octahedron containing the rare-earth ion changes little with pressure (up to 12 GPa). It is shown that the dependence of the unit cell volume on pressure is described by the Birch-Murnaghan equation of state of the third order.

scholarly journals C2: An Asymmetric Specie ?

2020 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Chemical Bond ◽  
Raman Spectra ◽  
Density Functional ◽  
Functional Approach ◽  
Ir And Raman Spectra ◽  
Basis Set ◽  
Ir And Raman

<p> The present work is another contribution to a better understanding of the chemical bond in C<sub>2</sub>. Several density functional approach/basis set provided calculated IR and Raman spectra with simultaneous active bands. Hence, the hypothesis of electronic asymmetry in C<sub>2</sub> [1] was reinforced. </p>

Chemical adsorption of salicylate on silver - A systematic approach to the interpretation of surface-enhanced vibrational spectra

2004 ◽  
Vol 82 (6) ◽  
pp. 987-997 ◽  
Author(s):  
P J.G Goulet ◽  
R F Aroca
Keyword(s):  
Salicylic Acid ◽  
Raman Spectra ◽  
Vibrational Spectra ◽  
Density Functional ◽  
Ir And Raman Spectra ◽  
Chemical Adsorption ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering ◽  
Ir And Raman

In this work, surface-enhanced vibrational spectroscopy and normal vibrational spectroscopy as well as density functional theory (DFT) computational methods have been employed to investigate the nature of the chemical adsorption and orientation of the surface species generated from salicylic acid at silver surfaces. The structure of salicylic acid and its IR and Raman spectra are determined at the B3LYP/6-311+G(d,p) level of theory. These results are used in the assignment of the vibrational spectra. Surface-enhanced Raman scattering (SERS) spectra obtained from silver island films thinly coated with salicylic acid confirm chemical adsorption on the Ag nanostructures. To probe the nature of this surface complex, the optimized geometries and IR and Raman spectra of two model salicylate-silver complexes (Ag1 and Ag2) were calculated at the B3LYP/Lanl2DZ level of theory. It was found that good agreement exists between experimentally observed SERS spectra and the simulated SERS spectra of a complex with the salicylate monoanion bound to a Ag+ ion through its carboxylate group (Ag1). The carboxylate silver salt of salicylic acid (essentially the Ag1 complex) was also prepared, and its IR and Raman spectra were recorded for comparison with the surface-enhanced vibrational spectra. These results, along with the application of surface selection rules, suggest that salicylic acid is deprotonated at silver surfaces, interacting through its carboxylate group alone, and is preferentially in a tilted head-on orientation.Key words: chemisorption, salicylic acid, silver, density functional theory, surface-enhanced Raman scattering, reflection-absorption IR spectroscopy, surface-enhanced IR absorption.

Ab initio spectroscopy of water under electric fields

2019 ◽  
Vol 21 (38) ◽  
pp. 21205-21212 ◽  
Author(s):  
Giuseppe Cassone ◽  
Jiri Sponer ◽  
Sebastiano Trusso ◽  
Franz Saija
Keyword(s):  
Ab Initio ◽  
Raman Spectra ◽  
Electric Fields ◽  
Liquid Water ◽  
High Frequency ◽  
Water Structure ◽  
Ir And Raman Spectra ◽  
Bulk Liquid ◽  
Librational Mode ◽  
Ir And Raman

IR and Raman spectra of bulk liquid water under intense electric fields reveal the contraction of both spectra and the onset of a novel high-frequency librational mode band. Moreover, the water structure evolves toward “ice-like” arrangements.

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