XIV
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International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
348
T9: P–22
Analysis of atom transfer between cages in type-I silicon clathrates
based on vibrational spectroscopy – DFT calculations
Wojciech Szczypka
1
, and Andrzej Koleżyński
1
1
Faculty of Materials Science and Ceramics, AGH University of Science and Technology, al.
Mickiewicza 30, 30-059 Kraków, Poland, e-mail: szczypka@agh.edu.pl
The family of silicon clathrates are attracting great attention because of noteworthy
thermoelectric properties, but also in the fields of superconductivity, wide band gap
semiconductors and electrochemical applications [1–2]. The structure of type-I clathrate consists
of two Si
20
and six Si
24
cages (Fig. 1), inside which introduced guest atoms may have
significantly greater freedom of movement than atoms building up clathrate’s framework.
In this work several structures of type-I silicon clathrate filled with alkali metals, Me
x
Si
46
,
were studied theoretically using CRYSTAL14 package [3] within density functional theory
(DFT). Harmonic vibrational frequencies with Raman intensities were calculated after full
geometry optimisation of analysed structures.
For chosen modes calculations were done for structures with atomic displacements
exaggerated in such a way that guest atom reached saddle point between two adjacent cages. In
addition, typical calculations at transition state were performed. Both methods were compared in
order to verify, if such simplified method based on analysis of harmonic vibrations may provide
useful information about atom transfer between cages and hence ion transport through the type-I
silicon clathrate structure.
Fig. 1. Structure of type-I silicon clathrate with guest atoms inside cages.
Keywords: silicon clathrates; transition state; DFT calculations
Acknowledgment
This research was financed by Polish Ministry of Science and Higher Education from the budget for science
in the years 2015-2019, as a research project under the program "Diamond Grant" (grant no. DI2014
019144) and supported in part by PL-Grid Infrastructure.
References
[1] J. Yang, J.S. Tse, J. Mater. Chem. A. 1 (2013) 7782.
[2] T. Kume, T. Koda, S. Sasaki, H. Shimizu, J.S. Tse, Phys. Rev. B. 70 (2004) 52101.
[3] R. Dovesi et al., Int. J. Quantum Chem. 114 (2014) 1287.
XIV
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International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
349
T9: P–23
Line mixing effect in the ν
2
and ν
4
bands of PH
3
perturbed by H
2
:
analyses and theoretical calculations
Salem Jamel
1
, Dhib Mohamed
2
, and Aroui Hassen
2
1
Department of Physics, Faculty of science, 2100 Gafsa, Tunisia, e-mail: sfjamel1@yahoo.fr
2
Department of Chemical Physics, Ecole Nationale Supérieure d’Ingénieurs, 5 Avenue Taha Hussein
1008 Tunis, Tunisia
The collisional spectroscopic parameters: intensities, linewidths, lineshifts and line mixing
are all grouped together in the collisional relaxation matrix. To analyze the collisional process
related to the line coupling in the case of phosphine (PH
3
) perturbed by hydrogen (H
2
), we take
the measurements used in the work [1] to study them with more precision. These measurements
are carried out using a tunable diode-laser spectrometer in the ν
2
and ν
4
bands of PH
3
perturbed
by H
2
at room temperature.
The recorded spectra are fitted by three profiles: Voight Profile (VP), Speed-dependent hard
collision model of Rautian and Sobelman Profile (SDRP) and Rosenkranz Profile. The line
mixing coefficients deduced through the multi-pressure non-linear least squares fitting of
Rosenkranz profile taking into account coupling effect, are compared with theoretical
calculations bases on a semiclassical state-to-state model of interacting linear molecules. The
intermolecular potential used in this work is the electrostatic potential in addition to the atom–
atom Lennard-Jones contribution.
Keywords: line mixing; phosphine; hydrogène
References
[1] J. Salem, Gh. Blanquet, M. Lepère, H. Aroui, J. Mol. Spectr. 297 (2014) 58.
XIV
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International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
350
T9: P–24
Analysis of PH
3
spectra in the ν
2
and ν
4
bands
and self-shifting parameters
Salem Jamel
1
1
Department of Physics, Faculty of science, 2100 Gafsa, Tunisia, e-mail: sfjamel1@yahoo.fr
The collisional broadening and shifting parameters are described by the diagonal elements of
the collisional relaxation matrix. The study of the isolated lines where the interference effect
with the off-diagonal elements of the relaxation matrix close to zero is neglected reduces the
number of correlated collisional parameters. To analyze the spectra recorded for phosphine
(PH3) self-perturbed using a tunable diode-laser spectrometer in the ν
2
and ν
4
bands at room
temperature; we have used different profiles such as Voigt Profile (VP), the hard collision
profile of Rautian and Sobelman (RP) [1] and the speed-dependent hard collision model of
Rautian and Sobelman (SDRP) [2]. To fitting the experimental spectra, some physical effects
such as the Dicke narrowing and the speed-dependence effects on the spectra are discussed.
Also, line shifts coefficients with a reasonable uncertainty are extracts in
Q
R of the ν
2
band and
P
P and
R
P branches of the ν
4
band of PH
3
.
To considering the electrostatic contributions dominating the anisotropic potential for this
molecule (PH
3
), we have testing a semi-classical theoretical calculations based on ATC theory
[3] and ameliorate in others work [4]. These spectral parameters are compared with other results
available in literature.
Keywords: line shifts; phosphine; analyses; theoretical calculations
References
[1] S.G. Rautian, I.I. Sobelman, Soviet Physics Uspekhi 9 (1967) 701.
[2] B. Lance, G. Blanquet, J. Walrand, J-P. Bouanich, J. Mol. Spectrosc. 185 (1997) 262.
[3] C.J. Tsao, B. Curnutte, J. Quant. Spectrosc. Ra. 2 (1961) 41.
[4] J. Buldyreva, N. Lavrentieva. V. Starikov, London: World Scientific, Imperial College Press; 2010.
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