Pressure and temperature driven phase transitions in HgTe quantum wells

We present theoretical investigations of pressure and temperature driven phase transitions in HgTe quantum wells grown on CdTe buffer. Using the 8-band \textbf{k$\cdot$p} Hamiltonian we calculate evolution of energy band structure at different quantum well width with hydrostatic pressure up to 20 kBar and temperature ranging up 300 K. In particular, we show that in addition to temperature, tuning of hydrostatic pressure allows to drive transitions between semimetal, band insulator and topological insulator phases. Our realistic band structure calculations reveal that the band inversion under hydrostatic pressure and temperature may be accompanied by non-local overlapping between conduction and valence bands. The pressure and temperature phase diagrams are presented.Comment: 9 pages, 8 figures + Supplemental material (5 pages

The Process of Acetonitrile Synthesis over γ-Al[2]O[3] Promoted by Phosphoric Acid Catalysts

The influence of principal parameters (reaction temperature, ratio of acetic acid and ammonia, composition of reactionary mixture and promotion of catalysts) on the selectivity and yield of the desired product was studied in the reaction of catalytic acetonitrile synthesis by ammonolysis of acetic acid. The processing of [gamma]-Al[2]O[3] by phosphoric acid increases amount of the centers, on which carries out reaction of acetamide dehydration. The kinetic model of a limiting stage of reaction - the acetamide dehydration to acetonitrile was suggested. In the process of ammonolysis of acetic acid it was demonstrated that the use of catalysts promoted by phosphoric acid and ratio NH[3]:CH[3]COOH=(3-4):1 at temperatures of a reactor 360-390°С leads to the increase of acetonitrile productivity to 0.7-0.8 g/cm{3}·h and allows to minimize formation of by-products

Engineering of Low-Loss Metal for Nanoplasmonic and Metamaterials Applications

We have shown that alloying a noble metal (gold) with another metal (cadmium), which can contribute two electrons per atom to a free electron gas, can significantly improve the metals optical properties in certain wavelength ranges and make them worse in the other parts of the spectrum. In particular, in the gold-cadmium alloy we have demonstrated a significant expansion of the spectral range of metallic reflectance to shorter wavelengths. The experimental results and the predictions of the first principles theory demonstrate an opportunity for the improvement and optimization of low-loss metals for nanoplasmonic and metamaterials applications.Comment: 14 Pages, 4 figure

Transport of covariance matrices in the inhomogeneous magnetic field of the ATLAS experiment by the application of a semi-analytical method

In this paper we study the transport of track parameter covariance matrices - the so-called error propagation - in the inhomogeneous magnetic field of the ATLAS experiment. The Jacobian elements are transported in parallel with the track parameters, avoiding the inherent need of any purely numerical scheme of propagating a set of auxiliary tracks. We evaluate the quality of the transported Jacobians by a very thorough, purely numerical approach of obtaining the same derivatives, providing a quantitative understanding of the effects of including gradients of energy loss and the magnetic field on the accuracy of the error propagation. Irrespective of the accuracy of the underlying track parameter propagation, the method of parallel integration of the derivatives is demonstrated to be significantly faster than even the simplest numerical scheme. The error propagation presented in this paper is part of the simultaneous track and error propagation (STEP) algorithm of the common ATLAS tracking software

Track parameter propagation through the application of a new adaptive Runge-Kutta-Nystrom method in the ATLAS experiment

In this paper we study several fixed step and adaptive Runge-Kutta methods suitable for transporting track parameters through an inhomogeneous magnetic field. Moreover, we present a new adaptive Runge-Kutta-Nystrom method which estimates the local error of the extrapolation without introducing extra stages to the original Runge-Kutta-Nystrom method. Furthermore, these methods are compared for propagation accuracy and computing cost efficiency in the simultaneous track and error propagation (STEP) algorithm of the common ATLAS tracking software. The tests show the new adaptive Runge-Kutta-Nystrom method to be the most computing cost efficient