The thermodynamic properties and anharmonic effects in atomic vibration have been analyzed based on the obtained temperature-dependent XAFS cumulants where the anharmonicity
causing thermal expansion and the MSRD component perpendicular to bond direction have been discussed in detail.
Although the experiments on the material of this work were performed with initial elastic deformation, the degree of anharmonicity
increases with increasing bending according to (1) (Figure 8).
where x is anharmonicity
factor and n is the integer vibration quantum number.
Since tunnelling effects can be safely neglected for a single-well potential, we can make unambiguous manifestation of an effect of anharmonicity
in the confining potential on differences between computational results obtained from the two distinct hybrid schemes.
Dorogokupets, "All-electron and pseudopotential study of MgO: equation of state, anharmonicity
, and stability," Physical Review B, vol.
Ab initio calculations follow the approximation that the chemical bonds are elastic, but it is not the case especially at higher range of frequencies due to anharmonicity
of vibrations .
Sapriel, "Raman investigation of anharmonicity
and disorder-induced effects in Ga1-xAlxAs epitaxial layers," Physical Review B, vol.
It is well known that calculated Hartree-Fock (HF) IR spectra must be scaled to account for the effects of anharmonicity
This is due to the deficiency of the electron-electron interaction considered and the neglect of anharmonicity
when calculating the vibrational frequencies, and the experimental data are almost adjusted with the simulated one using the scaling factors [9-11].
It covers the basis required for quantum oscillator studies, single quantum harmonic oscillators, anharmonicity
, oscillator populations in thermal equilibrium, quantum normal modes of vibration, damped harmonic oscillators, and vibrational spectroscopy.