In this work, we present the broadband dielectric spectroscopy results of Ca-modified BaZrxTi1-xO3 (x = 0.5; 0.6). The goal of the work is to understand if the relaxor ferroelectric properties of BZT are affected by the calcium substitution at the A-site of the perovskite lattice. The tolerance factor of calcium ions is below 1 so they are supposed to introduce a larger lattice distortion. Thus, we carefully investigate two BZT (BZT50 and BZT40) compositions with 10% of calcium. To assess the influence of the substitution, we analyze the dielectric spectra and Vogel-Fulcher behaviour of mean relaxation time. This data is compared with the data of parental compositions that are available in the literature.
In this study, using spin-polarized density functional theory (DFT) calculations, a detailed investigation is conducted into the structural, electronic, magnetic and optical properties of Zn1-xNixO ternary alloys in the wurtzite, zinc-blende and rocksalt crystal phases. The calculated lattice parameters show a a slight nonlinear variation with Ni concentration, indicating a minor deviation from Vegard's law in the intermediate composition range. Electronic structure calculations reveal that all investigated alloys preserve their semiconducting nature throughout the entire composition range, although both the type and value of the band gap depend strongly on the crystal phase and Ni content. Charge density analysis suggests that pure ZnO exhibits a partially covalent bonding character, that gradually weakens as the concentration of Ni increases. The magnetic results show that NiO possesses a total magnetic moment of 4 mu B per unit cell in the wurtzite phase and 2 mu B per unit cell in the zinc-blende and rocksalt phases. Optical investigations indicate that both alloying and phase transitions significantly modify the optical response of the material. Notably, the alloys exhibit a strong absorption over a broad photon energy range, with the rocksalt phase showing the highest absorption. The static refractive indices for various compositions and crystal structures are also reported.
In order to ascertain the precise atomic characteristics, it is important to incorporate a wide range of electron correlations in the computational analysis. However, it is important to note that undertaking such studies will result in substantial increases of the configuration state function expansions. The present publication, as well as the series of articles that have been published by G. Gaigalas, P. Rynkun, and L. Kitovien & edot;, are dedicated to the analysis and resolution of the problem in question. In this series, a method was developed based on second-order perturbation theory to identify the most important core-valence, core, core-core, and valence-valence correlations. The method under discussion is based on a combination of the relativistic configuration interaction method and the stationary second-order Rayleigh-Schr & ouml;dinger many-body perturbation theory in an irreducible tensorial form. In this study, the method is further expanded to encompass additional core-valence electron correlations of the third and fourth types. Conversely, the correlations that are not encompassed by perturbation theory are addressed in a conventional manner. This method can be used to calculate the properties of an atom or ion with any number of valence and core electrons. As an example of its application, the atomic calculations of the energy structure and lifetime for Ne II are presented.
The creation of nanocomposite materials based on fullerene and a rare metal with unique hybrid properties is promising for use in chemical sensors, photocatalytic devices and energy storage devices. A nanocomposite thin film containing fullerene C60 and silver (Ag) nanoparticles was synthesized by introducing an Ag nanoparticle into the fullerene matrix using thermal evaporation of the solution. The morphological and optical properties of both solutions consisting of fullerene and silver and the C60-Ag nanocomposite at different concentrations of the components were studied using optical absorption, refractometry, dynamic light scattering, Raman spectroscopy and electron microscopy. The surface plasmon resonance (SPR) band of the C60-Ag nanocomposite under different conditions was determined. A significant redshift (similar to 12 nm) of the SPR band was observed with annealing a thin film at 60 degrees C.
The geometric configuration of dangling bonds (DBs) - one of the most abundant paramagnetic defects in nanodiamonds (NDs) - is investigated by applying the global optimization algorithm (GOAT). A total of more than five million geometry optimization runs are carried out to search for the lowest-energy conformers of DBs introduced into hydroxylated and aminated NDs. An analysis of over 3,000 electronic g-tensor calculations performed for the obtained structures shows that only three unique DB types are present in octahedrally shaped C35(OH)36 and C35(NH2)36 nanoparticles, enabling future studies on similar NDs with fully functionalized surfaces to consider a relatively small number of DBs and thereby save computational time and resources. It is also revealed that the arithmetically averaged isotropic g-shifts from the geometries of the standard optimization agree well with the GOAT results, although the behaviour of individual DBs is not properly captured.
