Frequencies and polarization vectors of phonons: Results from force constants which are fitted to experimental data or calculatedab initio

2012 ◽  
Vol 86 (17) ◽  
Author(s):  
Christian Illg ◽  
Bernd Meyer ◽  
Manfred Fähnle
Keyword(s):  
Experimental Data ◽  
Force Constants

scholarly journals A Quantum Chemistry Approach to the Force Fields of the Thionyl and Selenyl Halides, SOX2 and SeOX2

2007 ◽  
Vol 62 (12) ◽  
pp. 1491-1496
Author(s):  
Lis E. Fernández ◽  
Eduardo L. Varetti
Keyword(s):  
Experimental Data ◽  
Quantum Mechanics ◽  
Quantum Chemistry ◽  
Force Fields ◽  
Internal Force ◽  
Vibrational Frequencies ◽  
Force Constants ◽  
Definition Of ◽  
Theoretical Results

Force fields and vibrational frequencies were calculated for the molecules SOX2 and SeOX2, with X = F, Cl, Br, using DFT techniques. The previously available experimental data and assignments for the six molecules were confirmed by the theoretical results. These data were subsequently used in the definition of the corresponding scaled quantum mechanics (SQM) force fields. A comparison of the obtained internal force constants is made with results reported by other authors for the studied species.

LATTICE DYNAMICS OF NICKEL

1967 ◽  
Vol 45 (5) ◽  
pp. 1655-1660 ◽  
Author(s):  
S. P. Singh
Keyword(s):  
Experimental Data ◽  
Specific Heat ◽  
Debye Temperature ◽  
Density Of States ◽  
Elastic Constants ◽  
Lattice Dynamics ◽  
Vibration Spectrum ◽  
Force Constants ◽  
Effective Force ◽  
Good Agreement

The vibration spectrum of the nickel lattice has been calculated using the simple de Launay method with values for the effective force constants determined from published experimental data for the elastic constants. The density-of-states curve reproduces the same general features found by Birgeneau et al. (1964) using a fourth-neighbor model. The Debye temperature at 0 °K is found to be 474 °K in good agreement with the experimental value of 468 °K, and the calculated variation of the Debye temperature with temperature agrees quite well with that deduced from measurements of the specific heat.

Molecular Vibrations of Cubane and Its Deuterated Derivatives

1983 ◽  
Vol 38 (11) ◽  
pp. 1248-1262 ◽  
Author(s):  
S. J. Cyvin ◽  
B. N. Cyvin ◽  
J. Brunvoll
Keyword(s):  
Experimental Data ◽  
Iteration Method ◽  
Vibrational Frequencies ◽  
Force Constants ◽  
Molecular Vibrations ◽  
Mean Amplitudes Of Vibration ◽  
First Order ◽  
Amplitude Correction ◽  
Harmonic Field ◽  
Simultaneous Fitting

A harmonic field for cubane is developed by means of the following experimental data from literature: vibrational frequencies for C8H8, sym-C8H6D2, sym-C8H2D6 and C8D8, in addition to three Coriolis constants of C8H8. As a part of this analysis a new iteration method was developed for simultaneous fitting of vibrational frequencies and first-order Coriolis constants of a threedimensional symmetry block. The force constants were used to calculate the vibrational frequencies of all the twenty existing partially deuterated cubanes, in addition to the unsubstituted (C8H8) and perdeuterated (C8D8) molecules. Also the first-order Coriolis constants, mean amplitudes of vibration and perpendicular amplitude correction coefficients for selected cubane molecules are reported

Das Kraftfeld von SF4 / The Force Field of SF4

1980 ◽  
Vol 35 (9) ◽  
pp. 1137-1142 ◽  
Author(s):  
Wolfgang Sawodny ◽  
Karl Birk ◽  
Karl O. Christe
Keyword(s):  
Experimental Data ◽  
Force Field ◽  
Ab Initio ◽  
Force Constants ◽  
Basis Set ◽  
Valence Force ◽  
Valence Force Field

As it proved impossible, to compute a unique and meaningful General Valence Force Field for SF4 from the known experimental data, this was realized by an ab initio cal­culation using a basis set of 3-3-21 + 1 d G functions for the S-, and 4-21 G functions for the F-atom. The values of the stretching force constants are f (S-Feq): 5.36 mdyn/Å, f(S-Fax): 3.25 mdyn/Å. Problems of assignment of the deformational modes could be settled conclusively.

Normal Coordinate Analysis of Nitrogentrichloride

1972 ◽  
Vol 27 (5) ◽  
pp. 865-867
Author(s):  
S. N . Rai ◽  
Badri Rai ◽  
K. P. R . Nair ◽  
S. N. Thakur
Keyword(s):  
Experimental Data ◽  
Force Fields ◽  
Vibrational Frequencies ◽  
Normal Coordinate Analysis ◽  
Force Constants ◽  
Recent Experimental Data ◽  
Normal Coordinate ◽  
Nitrogen Trichloride

Abstract The intramolecular force fields of nitrogen trichloride have been determined using the recent experimental data on the vibrational frequencies. Three different methods have been used for the evaluation of force constants. The results ob-tained are quite consistent

Ab-Initio and PCILO Calculations of Diamond Clusters and the Corresponding Saturated Hydrocarbons

1978 ◽  
Vol 33 (3) ◽  
pp. 358-365
Author(s):  
H. P. Waschi ◽  
H. Stoll ◽  
H. Preuß
Keyword(s):  
Experimental Data ◽  
Total Energy ◽  
Ab Initio ◽  
Closed Shell ◽  
Force Constants ◽  
Basis Sets ◽  
Saturated Hydrocarbons ◽  
Bond Lengths ◽  
Hartree Fock

AbstractClosed-shell diamond clusters and saturated hydrocarbons are investigated with PCILO and ab-initio Hartree-Fock using very small basis sets. The ab-initio distances for the C-C bonds differ by 5% or less, the PCILO distances by 2 to 2.5% from experimental data. The dependence of bond lengths and force constants on the cluster construction is studied. For selected molecules the effect of intermolecular rotations on the total energy is considered.

scholarly journals Berechnung kinetischer Isotopeneffekte für die Reaktion von Methyljodid mit Hydroxid-Ion

1966 ◽  
Vol 21 (9) ◽  
pp. 1385-1390 ◽  
Author(s):  
A. V. Willi
Keyword(s):  
Experimental Data ◽  
Transition State ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Force Constants ◽  
Linear Functions ◽  
Bending Force ◽  
Small Influence ◽  
Carbon Isotope Effect ◽  
Secular Equations

Kinetic carbon-13, deuterium, and oxygen-18 isotope effects are calculated from force constants for the SN2 reaction of CH3I with OH-. The secular equations for the vibrational frequencies of reactants and transition states are solved on an IBM 7094 computer. Values for 7 force constants of the planar CH3 moiety in the transition state (with an sp2 atom) are obtained by comparison with suitable stable molecules. The stretching force constants ƒCO = ƒ11, ƒCI = ƒ22, and ƒ12 in the transition state are chosen as linear functions of x, the degree of bond making and bond breaking, with the aid of eqs. (1) and (2).The carbon isotope effect as a function of x exhibits a flat maximum near x=0.6. If the bending force constants ƒHCO and ƒHCI are kept constant, k12/k13 is significantly lower than its maximum value only for values of x ≦ 0.3 and x ≧ 0.8. There is only a small influence of x on the deuterium isotope effect, kH/kD (compare rates of CH3I and CD3I). However, kH/kD) is strongly dependent on ƒHCO and ƒHCI . The oxygen-18 isotope effect decreases with increasing x. Experimental data of the D isotope effect — if they were available — could be used to adjust the bending force constants ƒHCO and ƒHCI (— or to adjust ƒHCO if ƒHCI is held constant). The degree of unsymmetry of the transition state could then be estimated with the aid of the C isotope effect. Experimental data of the O isotope effect would supply information on the direction of the unsymmetry — which is needed for a distinction between 2 possible values of x —. There is approximate agreement between the calculated and the experimental temperature dependence of the carbon-13 isotope effect.

Microdiffraction Patterns of Small Metallic Particles II; Theoretical Analysis

1982 ◽  
Vol 40 ◽  
pp. 668-669
Author(s):  
A. Gómez ◽  
P. Schabes-Retchkiman ◽  
M. José-Yacamán ◽  
T. Ocaña
Keyword(s):  
Experimental Data ◽  
Electron Diffraction ◽  
Theoretical Analysis ◽  
Size Range ◽  
Dynamical Theory ◽  
Metallic Particles ◽  
Splitting Effect

The splitting effect that is observed in microdiffraction pat-terns of small metallic particles in the size range 50-500 Å can be understood using the dynamical theory of electron diffraction for the case of a crystal containing a finite wedge. For the experimental data we refer to part I of this work in these proceedings.

Sign in / Sign up

Export Citation Format

Share Document