Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Born-Huang approximation.The numerical results for sev-eral Ⅱ-Ⅵ and Ⅲ-Ⅴ compound systems are performed,and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs,GaPxAs1-x,ZnSxSe1-x,GaAsxSb1-x,GaxIn1-xP,and ZnxCd1-xS as examples are given and discussed.The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics,and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.
Based on ab initio total energy calculations,the structural,electronic,mechanic,and magnetic properties of PdH x are investigated.It is found that bulk modulus of PdH x is larger than the metal Pd with the hydrogen storage except Pd 4 H 2.The calculated results for the magnetic moments show that the hydrogen addition weakens the magnetic properties of the PdH x systems.A strong magneto-volume effect is found in PdH x structures as well as Pd.The transition from paramagnetism to ferromagnetism is discussed.The corresponding densities of states for both structures are also shown to understand the magnetic behaviour.
The variational method and the effective mass approximation are used to calculate the phonon effects on the hydrogenic impurity states in a cylindrical quantum wire with finite deep potential by taking both the couplings of the electron-confined bulk longitudinal optical(LO) phonons and the impurity-ion-LO phonons into account.The binding energies and the phonon contributions are calculated as functions of the transverse dimension of the quantum wire.The results show that the polaronic effect induced by the electron-LO phonon coupling and the screening effect induced by the impurity-ion-LO phonon coupling tend to compensate each other and the total effects reduce the impurity binding energies.
