Search

In this report, the problem of obtaining and using nanocomposite materials for radio networks of the optical and terahertz frequency bands is addressed. Nanoporous structures of anodized aluminum oxide Al2O3 with 40 and 85 nm pore diameters were prepared. We were succeeded in synthesis of a nanocomposite material composed of nanowires and nanotubes of the crystalline material KH2PO4, embedded into the pores of Al2O3 matrix. As a result, the created nanocomposite material Al2O3:KH2PO4 can be potentially used as an active medium in the optical range, as well as a decelerating material and element of antenna-feeder devices of radio networks. [ABSTRACT FROM AUTHOR]

The mean atomic kinetic energies of the proton, Ke(H), and of the deuteron, Ke(D), were calculated in moderate and strongly hydrogen bonded (HB) systems, such as the ferro-electric crystals of the KDP type (XH2PO4, X = K, Cs, Rb, Tl), the DKDP (XD2PO4, X = K, Cs, Rb) type, and the X3H(SO4)2 superprotonic conductors (X = K, Rb). All calculations utilized the simulated partial phonon density of states, deduced from density functional theory based first-principle calculations and from empirical lattice dynamics simulations in which the Coulomb, short range, covalent, and van der Waals interactions were accounted for. The presently calculated Ke(H) values for the two systems were found to be in excellent agreement with published values obtained by deep inelastic neutron scattering measurements carried out using the VESUVIO instrument of the Rutherford Laboratory, UK. The Ke(H) values of the M3H(SO4)2 compounds, in which the hydrogen bonds are centro-symmetric, are much lower than those of the KDP type crystals, in direct consistency with the oxygen-oxygen distance ROO, being a measure of the HB strength. [ABSTRACT FROM AUTHOR]

Lattice dynamics of CsH 2 PO 4 and CsD 2 PO 4 crystals has been studied by density functional theory in two structural phases ( P 2 1 / m and P 2 1 ). The bulk crystal structure, electronic band structure, phonon spectra in different symmetry points and directions of Brillouin zone, density of states and partial density of states have been calculated. The lattice instability at Brillouin zone boundary close to (1/2, 0, 1/2) and (0, 0, 1/2) points has been found in paraelectric P 2 1 / m phase of both title crystals. The detailed interpretation of spectroscopic experimental data is performed basing on simulated vibrational spectra. The matrices of elastic constants, piezoelectric coefficients and temperature dependent heat capacity are calculated. [ABSTRACT FROM AUTHOR]

The simulation of CsH 2 PO 4 lattice dynamics in paraelectric phase was carried out within the semi-phenomenological approach. Phonon frequencies at Brillouin zone centre, LO-TO splitting of polar modes, phonon density of states, partial density of states associated with a certain type of atoms and specific heat were calculated. A reasonable agreement between the computed values and experimental data reveals an acceptability of the suggested approach. [ABSTRACT FROM AUTHOR]

Within the modified four-sublattice model of RbHSO4 with taking into account the piezoelectric coupling to the strains εi, ε4, ε5, and ε6, the polarization components, static and dynamic dielectric permittivity of clamped and free crystal are calculated in the mean field approximation. At the proper choice of the values of the theory parameters, a satisfactory quantitative description of the available experimental data is obtained. [ABSTRACT FROM AUTHOR]