Electrical Transport in Polyvalent Liquid Bismuth and Antimony Metals

Accurate assessment of electrical transport for heavy polyvalent metals pause challenge due to complex electronic band structure, where s-wave scattering theory due to Ziman is failed. Improving schemes like t-matrix resistivity and self-consistent approach are proposed. In the present study, we employ selfconsistent approach to compute electrical resistivity (ρ) in liquid Bi and Sb at different temperatures (T). Structural input is estimated through charged hard-sphere reference system. Electron-ion interaction is modelled by modified empty-core pseudopotential including electron exchange and correlation effects. Since only two parameters are independent, as the core radius RC (= 0.51 RaZ − 1⁄3) is a theoretical input, we have tuned, once and for all, the single parameter to find ρ at melting temperature. The same set of parameters is used to deduce high-T resistivity, thermal conductivity and thermo-electric power. Overall good agreement is observed for transport properties for both metals. The present fitting scheme and so deduced results are discussed in comparison with other findings

Quasiharmonic r–space Computational Scheme for Phonon Dynamics: Case Study of Calcium Oxide

The role of phonons is important in accounting various properties of materials. Crystal potential being an anharmonic function of volume, variations are seen in phonon derived properties with a change in volume. In the present work, we employ an approximate technique of expanding phonon frequencies using Taylor series expansion upto second-order in volume to calculate the volume dependent phonon frequencies of CaO in B1 and B2 phases. Equilibrium properties are obtained by fitting Murnaghan EoS to first principles DFT based results, however. The mode Grüneisen parameter and concavity parameter are computed with the help of present ab initio phonon frequencies for both the phases. Their volume dependence are estimated analytically using the proposed scheme. We find that phonon frequencies increase by decreasing volume. Analytically calculated volume dependent phonon frequencies are compared in reasonable agreement with the frequencies obtained directly using DFT for B1-phase. Thus, the present r–space computational scheme of deriving volume dependent phonon frequency proves to be an alternative to overcome lengthy phonon calculations

Theoretical Investigations of Lattice Dynamics and Dynamical Elastic Constants of Rh0.6Pd0.4 and Rh0.2Pd0.8 Binary Alloys Using Transition Metal Pseudopotential

The experimental and theoretical studies of various properties of transition metals alloys are important in the material science research. Inspired by such fact, in the present communication we have carried out theoretical studies of lattice dynamics and dynamical elastic constants of Rh0.6Pd0.4 and Rh0.2Pd0.8 using transition metal pseudopotential. The form of the pseudopotential used in the present calculation is directly derived from generalized pseudopotential theory (GPT) and no phenomenology was used to construct pseudopotential in real space. The pseudopotential was found to be successful for the study of static, dynamic and transport properties of many transition metals. In absence of any experimental and theoretical studies first time we are presenting theoretical results of phonon dispersion for both the alloys which may be considered as prediction. Due to unavailability of experimental results, presently computed elastic constants are comparable with those studied recently by using Exact Muffin-Tin Orbitals method within the Perdew-Burke-Ernzerhof exchange-correlation approximation. Encouraged by present approach, we would like to extend it further for the remaining binary alloys of transition metals alloys

The Theoretical Study of Electron Dispersion of Some Liquid Metals Using Transition Metal Model Potential (TMMP)

In the present communication, we have proposed a simple method using which two parameters of Kumar’s pseudopotential can be reduced to effectively single parameter. Further the reliability of our proposed method is examined by carrying out electron dispersion curves (E(k) → k), Fermi energy (EF) and density of states at Fermi energy (N(EF)) for sixteen liquid metals. In absence of any experimental or theoretical results of aforesaid properties, our results will throw some light in the determination of interactions persisting in the liquid state of transition metals

Temperature Variation of Debye-Waller Factor and Mean Square Displacement for bcc Metals Using Density Based Pseudopotential

The variation of Debye-Waller factors and mean square displacements at different temperatures for simple bcc metals Li, Na, Rb and Cs is studied using pseudopotential proposed by Fiolhais et al. Comparison of computed theoretical values with experimental results is made and discussed. A reasonable agreement is found between our results and experimental data

The Study of Lattice Dynamics and Dynamical Elastic Constants for Calcium (Ca) and Strontium (Sr) in bcc Phase Using Pseudopotential Approach

Pseudopotential methods have been used successfully to understand static, dynamical and transport properties with good degree of agreement in condensed matter physics. In the present communication, we have investigated lattice dynamics of Ca and Sr in bcc phase using local pseudopotential due to George et al. The pseudopotential contains two parameters rc and which are determined from zero pressure condition. The computed results of phonon frequencies are in good agreement with experimental finding and maximum deviation for both the metals are about 10 % with experimental findings. Further, we have computed dynamical elastic constants (C11, C12 and C44) and bulk moduli (B) which are also comparable with experimental results and other theoretical results. Success of present study reveals that both metals behave as a simple metal rather than early transition metals and extra term for the inclusion of s-d hybridization is not required

The Comparative Study of Electrical Resistivity of bcc Liquid Transition Metals

In the present paper, we have used Ziman’s approach and transition matrix (t-matrix) approach to study the electrical resistivities of bcc liquid metals. By carrying out this study, we have verified the validity of our proposed pseudopotential extracted from generalized pseudopotential theory (GPT). Our theoretical results agree well with experimental results. Also, it has been verified that for transition metals tmatrix approach is more realistic and physically sound than Ziman approach

Search for supersymmetry using vector boson fusion signatures and missing transverse momentum in pp collisions at √s = 13 TeV with the ATLAS detector

This paper presents a search for supersymmetric particles in models with highly compressed mass spectra, in events consistent with being produced through vector boson fusion. The search uses 140 fb−1 of proton-proton collision data at √s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Events containing at least two jets with a large gap in pseudorapidity, large missing transverse momentum, and no reconstructed leptons are selected. A boosted decision tree is used to separate events consistent with the production of supersymmetric particles from those due to Standard Model backgrounds. The data are found to be consistent with Standard Model predictions. The results are interpreted using simplified models of R-parity-conserving supersymmetry in which the lightest supersymmetric partner is a bino-like neutralino with a mass similar to that of the lightest chargino and second-to-lightest neutralino, both of which are wino-like. Lower limits at 95% confidence level on the masses of next-to-lightest supersymmetric partners in this simplified model are established between 117 and 120 GeV when the lightest supersymmetric partners are within 1 GeV in mass

Search for charged Higgs bosons produced in top-quark decays or in association with top quarks and decaying via H±→τ±ντ in 13 TeV pp collisions with the ATLAS detector

Charged Higgs bosons produced either in top-quark decays or in association with a top quark, subsequently decaying via H±→τ±ντ, are searched for in 140  fb−1 of proton-proton collision data at s=13  TeV recorded with the ATLAS detector. Depending on whether the top quark is produced together with the H± decays hadronically or semileptonically, the search targets τ+jets or τ+lepton final states, in both cases with a τ-lepton decaying into a neutrino and hadrons. No significant excess over the Standard Model background expectation is observed. For the mass range of 80≤mH±≤3000  GeV, upper limits at 95% confidence level are set on the production cross section of the charged Higgs boson times the branching fraction B(H±→τ±ντ) in the range 4.5 pb–0.4 fb. In the mass range 80–160 GeV, assuming the Standard Model cross section for tt¯ production, this corresponds to upper limits between 0.27% and 0.02% on B(t→bH±)×B(H±→τ±ντ).</jats:p