Raman Spectrum and Force Constants of SF4

The crystal structure of diamond was first determined by Bragg in 1913 from X-ray photographs; the carbon atoms are arranged at the apices and median points of interlinked tetrahedra. Born (1914) derived expressions for the three elastic constants of diamond in terms of two force constants related to the valency bonds between neighbouring atoms. But, at that time, the only experimental data available were the compressibility and the Debye characteristic temperature 0, and precise determination of the valence force constants was not possible. Meanwhile, investigation of the optical properties of diamond had produced evidence for the existence of two distinct types, one with an absorption band at 8 [i in the infra-red, the other transparent at this point. Robertson, Fox & Martin (1934) took up this problem and found that absorption in the infra-red is associated with absorption in the ultra-violet; diamonds transparent at 8y transmit much farther into the ultra-violet. Both types of diamond have Bragg’s tetrahedral structure, the same refractive index, specific gravity, dielectric constant and electron diffraction. Their infra-red spectra are identical up to 7y, and the frequency shift of the principal Raman line is the same. The derivation of the elastic constants was again considered by Nagendra Nath (1934). He extended the theory to include central forces between second neighbours in the lattice. He also suggested that the frequency shift of the principal Raman line corresponds to the relative vibration of the two carbon atoms in the unit cell, along the line joining their nuclei. Raman and his collaborators have recently (1941) put forward a new theory of lattice dynamics according to which the vibrational spectrum of a crystal consists of a few discrete lines. This is in direct contradiction to the quasi-continuous vibrational spectrum predicted by classical or quantum mechanics. On this new theory there are eight fundamental frequencies of vibration for diamond; the values of these frequencies are deduced from the observed specific heat, ultra-violet absorption and Raman spectrum, which, it is claimed, cannot be explained by ‘orthodox’ lattice dynamics. Raman (1944) has suggested that there are, not two, but four types of diamond, two with tetrahedral symmetry and two with octahedral symmetry depending on the electronic configurations, but X-ray analysis gives no indication of this and the attempts of his school to explain the observed infra-red spectra on the basis of their new lattice theory have been, up to now, unsuccessful.

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The Raman Spectrum, Structure, Force Constants, and Thermodynamic Properties of Bromine Pentafluoride

The Journal of Chemical Physics ◽

10.1063/1.1700323 ◽

1952 ◽

Vol 20 (12) ◽

pp. 1830-1834 ◽

Cited By ~ 21

Author(s):

C. V. Stephenson ◽

E. A. Jones

Keyword(s):

Raman Spectrum ◽

Thermodynamic Properties ◽

Force Constants ◽

Spectrum Structure

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High-pressure effects on the Raman spectrum and the force constants of the rare-earth aluminium garnets (RE3Al5O12)

Journal of Physics Condensed Matter ◽

10.1088/0953-8984/14/15/303 ◽

2002 ◽

Vol 14 (15) ◽

pp. 3875-3890 ◽

Cited By ~ 7

Author(s):

K Papagelis ◽

J Arvanitidis ◽

G Kanellis ◽

S Ves ◽

G A Kourouklis

Keyword(s):

High Pressure ◽

Rare Earth ◽

Raman Spectrum ◽

Force Constants ◽

Pressure Effects ◽

High Pressure Effects ◽

The Rare Earth

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Raman spectra of mercury(I) and mercury(II) iodides in the solid state

Australian Journal of Chemistry ◽

10.1071/ch9682145 ◽

1968 ◽

Vol 21 (9) ◽

pp. 2145 ◽

Cited By ~ 22

Author(s):

RPJ Cooney ◽

JR Hall ◽

MA Hooper

Keyword(s):

Raman Spectrum ◽

Solid State ◽

Raman Spectra ◽

Factor Group ◽

Force Constants ◽

Unit Cells

The Raman spectrum of yellow Hg2I2 contains features at 110 and 192 cm-l assignable to Hg-Hg stretching and Hg-1 stretching respectively. The spectrum of yellow HgI2 at c. 150� shows bands at 33 cm-1 (I-Hg-1 bending) and 133 cm-1 (Hg-I stretching). The Raman shifts for red HgI2 are 24, 111, and 137 cm-l, attributable to I-Hg-1 bending, symmetric and asymmetric Hg-1 stretching respectively. Assignments are made on the basis of factor group analyses on the Bravais unit cells. Some force constants are calculated.

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Notizen:Schwingungsspektrum und Kraftfeld von Natriumhexanitrokobaltat

Zeitschrift für Naturforschung A ◽

10.1515/zna-1969-1035 ◽

1969 ◽

Vol 24 (10) ◽

pp. 1667-1668

Author(s):

Wolfgang Krasser

Keyword(s):

Raman Spectrum ◽

Force Field ◽

Point Group ◽

Vibrational Frequencies ◽

Force Constants ◽

Selection Rules ◽

Valence Force ◽

Valence Force Field ◽

Infrared Data

Abstract The Raman spectrum of Na3[Co(NO,)8] has been mea-sured in the range from 2000 to 50 cm 1 and the vibrational frequencies and their assignment are compared with infrared data already obtained. The force constants are calculated in the valence force field. With respect to vibrational spectro-scopy the CoN6-octaeder and the N02-group are assumed to be approximately two separate units. The justification of this approximation is discussed on the basis of the Raman spec-trum and the selection rules for the Symmetrie point group S6 of Na3 [Co (N02) 6]. Gefärbte Substanzen mit Absorptionsbanden im kurzwelligen sichtbaren Spektralbereich eignen sich vorzüglich für die Aufnahme des Raman-Spektrums, wenn man einen He —Ne-Laser mit seinem relativ lang-welligen Erregerlicht einsetzt 1 . Ein Molekül mit

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Kraftkonstanten des VO43- -Ions im Zirkon-Gitter [1] / Force Constants of the VO43- Ion in the Zircon Lattice

Zeitschrift für Naturforschung A ◽

10.1515/zna-1980-1019 ◽

1980 ◽

Vol 35 (10) ◽

pp. 1110-1111 ◽

Cited By ~ 10

Author(s):

Marta E. Escobar ◽

Enrique J. Baran

Keyword(s):

Rare Earth ◽

Raman Spectrum ◽

Force Field ◽

Force Constants ◽

Tetragonal Modification ◽

Valence Force ◽

Valence Force Field ◽

First Time ◽

Rare Earth Orthovanadates ◽

Zircon Type

Abstract Force Constants of the VO43- Ion in the different rare earth orthovanadates of the zircon type have been computed using a modified valence force field and recently reported Raman data. It is shown that the V-O bond strenghtening runs parallel to the unit cell contraction. The Raman spectrum of the tetragonal modification of LaVO4 is reported for the first time.

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