This work presents a method to determine the plasticity of clay soils using Fourier transform mid-infrared (FT-MIR) spectroscopy. Samples of mono- and polymineral soils of varying water contents are studied. The FT-MIR results are compared with the results obtained from standard Russian and international methods for the plasticity range. The correlation between the consistency of clay soils, when displaying their plastic properties, and the position of the Si–O stretching band in the FT-MIR spectra is established. The possibility of, and interest in, determining the plasticity characteristics of clay soils using mid-infrared spectroscopy is demonstrated: it yields effectively higher precision results compared to standard test methods. It is shown that the method of IR spectroscopy allows the fixing of the start and the completion of the series of “phase transitions” of the soil in the plastic and liquid state. The significant effect of the concentration of non-clay minerals on the Si–O ν line is that a moisture content curve is noticed, which may help to predict the clay content of the soil without undertaking XRD analysis.

We investigate the scattering of vibrational waves at the step interface between two structurally different waveguides, namely, one and two coupled atomic layers occupying the half spaces on either side of the step. The model presented is also instructive for the study of the scattering of surface phonons by random isolated steps in vicinal surfaces. The complexity of the scattering of vibrational waves, in contrast with coherent electron transport, which in part may be attributed to the vector character of the vibrational fields, is further enhanced in the present study owing to the intrinsic asymmetry of the system normal to the step as well as to its two-dimensional extended character. A detailed discussion of the reflection and transmission spectra is presented for the scattering processes in the two possible geometries normal to the step.

Unknown quantum electronic conductance across nanojunctions made of silicon-doped carbon wires between carbon leads is investigated. This is done by an appropriate generalization of the phase field matching theory for the multi-scattering processes of electronic excitations at the nanojunction and the use of the tight-binding method. Our calculations of the electronic band structures for carbon, silicon, and diatomic silicon carbide are matched with the available corresponding density functional theory results to optimize the required tight-binding parameters. Silicon and carbon atoms are treated on the same footing by characterizing each with their corresponding orbitals. Several types of nanojunctions are analyzed to sample their behavior under different atomic configurations. We calculate for each nanojunction the individual contributions to the quantum conductance for the propagatingσ,Π, andσ^∗electron incidents from the carbon leads. The calculated results show a number of remarkable features, which include the influence of the ordered periodic configurations of silicon-carbon pairs and the suppression of quantum conductance due to minimum substitutional disorder and artificially organized symmetry on these nanojunctions. Our results also demonstrate that the phase field matching theory is an efficient tool to treat the quantum conductance of complex molecular nanojunctions.

Coherent phonon scattering and transmission via a three-terminal junction in low-dimensional structures is investigated. The model system consists of two-dimensional crystalline wave-guides, constructed of double atomic chains that are joined together by a nanostructured T-shaped junction. The matching method theoretical approach is used to study the dynamics of the system. A calculation is presented for the coherent reflection and transmission scattering probabilities of the system phonons, as elements of a Landauer type scattering matrix. The scattering and transmission spectra via the T-shaped junction are analyzed as a function of the incident frequency per propagating mode of the perfect wave-guides. Our results show that the junction is an effective phonon splitter and suggest that its characteristics may be controlled by varying its nanometric parameters. Asymmetric Fano-like resonances are observed in the spectra which result from the coherent coupling between the localized modes of the T-shaped junction and the propagating modes of the wave-guides.