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In this study we attempted to model vacancy ordered half Heusler compounds with 18 valence electron count (VHH) derived from 19 VEC compounds such as TiNiSb such that the compositions will be Ti0.75NiSb, Zr0.75NiSb and Hf0.75NiSb with semiconducting behavior. The main motivation is that such a vacancy ordered phase not only introduce semi conductivity but also it will disrupt the phonon conducting path in HH alloys and thus reduces the thermal conductivity in turn enhancing thermoelectric figure of merit. In order to predict the formation energy (ΔHf) from material structure and composition we have used 4684 compounds for their ΔHf values as available in the material project database and trained a machine learning model with R2 value of 0.943. Using this model, we have predicted the ΔHf of a list of VHH. From the predicted VHH, we have selected Zr0.75NiSb and Hf0.75NiSb to validate the machine learning prediction using accurate DFT calculation. The calculated ΔHf for these two compounds from DFT calculation are found to be comparable with our ML prediction. The calculated electronic and lattice dynamics properties show that these materials are narrow-band gap semiconductors and are dynamically stable as their all-phonon dispersion curves are having positive frequencies. The calculated Seebeck coefficient, electrical conductivity as well as thermal conductivity, power factor, and thermoelectric figure of merit are analyzed. [ABSTRACT FROM AUTHOR]

Inelastic Neutron Scattering (INS) is an ideal tool to investigate the lattice dynamics (or phonons) of materials. It can be conducted not only experimentally, but also theoretically owing to the progress and advance in the computation method. The result from both theory and experiment can complement and confirm each other. We calculate phonon dispersion and phonon density of state of Copper single crystals using first-principle calculation. The phonon band was calculated from the Γ point to Λ and Σ direction. As expected from the presence of one atom within a primitive unit cell, there are three phonon branches consisting of one longitudinal acoustic (LA) and two transverse acoustic (TA) phonons. We then generate inelastic neutron scattering (INS) spectra using coherent approximation. The results are compared with the experimental data obtained from INS experiments using Indonesia's triple-axis spectrometer (TAS/SN1). The Q-E spectra from the simulation nicely coincide with the experimental data. This validates the quality of data and the performance of Indonesia's TAS/SN1 performance. It also opens the chance to conduct inelastic neutron scattering experiments simultaneously with theoretical analysis. [ABSTRACT FROM AUTHOR]

This work is devoted to the comparative study of the lattice specific heat of Cu(en)(H2O)2SO4, Cu(en)2SO4 and Cu(en)2CrO4, where en=ethylenediamine - C2H8N2. Previous studies on the effects of spatial anisotropy of exchange coupling within the magnetic layer showed that quasi-one-dimensional polymer structures based on Cu(II) ions, Cu(en)(H2O)2SO4 and Cu(en)2SO4 represent realizations of spin 1/2 Heisenberg model on the spatially anisotropic zig-zag square lattice and the dimerized square lattice, respectively. The substitution of S-Cr in isomorphic Cu(en)2SO4 and Cu(en)2CrO4 introduces differences in lattice specific heat. The description of the heat capacity of the lattice up to room temperature was carried out considering the contribution of acoustic phonons within the Debye model and optical phonons using Einstein approximation. Deviations of the Debye model from the lattice heat capacity are already observed above 15 K for all compounds, for Debye temperatures θD = 146 K, 101 K and 94 K for Cu(en)(H2O)2SO4, Cu(en)2SO4 and Cu(en)2CrO4, respectively. The effect of acoustic and optical modes on magnetic correlations in these systems is also discussed. [ABSTRACT FROM AUTHOR]

Crowdion being an interstitial type zero dimensional defect can form different complexes and clusters allowing the realization of effective propagation modes inaccessible for a single defect. For instance, recent studies of m- and n-crowdion configurations allowed one to figure out a set of specific features, including mass transfer, formation of voidions and remote vacancies. However, it is well known that the dynamics of defects in the lattice strongly depends on the interatomic potential as well as the lattice type of a considered structure. A significant part of the research on crowdions was carried out on bcc metals, since they are used in radiation, nuclear and other areas associated with extreme exposure. In this work, we perform the simulation of 4-crowdions in bcc W and fcc Ni in order to verify the presence of fundamental differences in the defect propagation dynamics in different lattices. [ABSTRACT FROM AUTHOR]

It has recently been shown that supersonic 2-crowdions are much more efficient at transferring mass along the crystal lattice compared to classical supersonic crowdions. This is so because, when a 2-crowdion moves, not one, but two atoms move at a high speed simultaneously, and the condition of self-focusing propagation is fulfilled for higher energies of the crowdion. It is interesting to analyze how interatomic potentials affect the self-focusing propagation of 2-crowdions. In this work, we investigate supersonic 2-crowdions in a bcc tungsten lattice by the molecular dynamics method using three different EAM interatomic poten- tials and the LAMMPS software package. It is shown that 2-crowdions propagate over much larger distances in tungsten modeled by potentials with stiffer repulsive cores (short-range parts). [ABSTRACT FROM AUTHOR]

Severe plastic deformation is known for its potential to obtain non-equilibrium solid solutions of metals, which under normal conditions are immiscible or have limited solubility. An important role in this process is played by the increased density of defects, which facilitates diffusion in the material during deformation. In particular, recently it was found that the application of ultra-severe plastic deformation can lead to dissolution of Zr atoms in aluminum, while the equilibrium phase diagram of these two metals shows that solid solution of Zr in Al is impossible. In the present work, we use molecular dynamics simulation to calculate the dependence of the lattice parameter of the Al-Zr solid solution as a function of the Zr concentration in the range from one to four atomic percent. It is found that our simulation results are in a reasonably good agreement with the experimental measurements of lattice parameter of Al-Zr solid solution obtained by ultra-severe plastic deformation. [ABSTRACT FROM AUTHOR]

A machine learning algorithm is used to propose three possible model phonon densities of states for a perspective thermoelectric material SnSe. Based on this and on the energy of the ground state calculated from the first principles, we develop a thermodynamic model of SnSe. The model is used to simulate temperature dependencies of the lattice properties of SnSe such as heat capacity, coefficient of thermal expansion, and bulk modulus. The anharmonicity of acoustic and optical phonons of SnSe is discussed. [ABSTRACT FROM AUTHOR]

Transition metal alloys are valuable in material science research. In the present communication, Transition Metal Pseudopotential has been used to investigate lattice dynamics in symmetry and non-symmetry directions for binary alloy RhxAg1-x (x = 0.6, 0.8). In absence of any neutron scattering data and theoretical results, we present theoretical results which may be considered as a prediction. Further, we have studied temperature variation of Debye temperature (θD) and dynamical elastic constants (C11, C12 and C44). As experimental results are not available for elastic constants, we have compared our results with the values obtained by first principles method. Presently obtained results are comparable with such theoretical results. [ABSTRACT FROM AUTHOR]

The transferability and predictivity of Fiolhais pseudopotential have been verified in the present communication for bcc Ca and Sr. Both the sets of parameters have been used to study lattice dynamics, dynamical elastic constants (C11, C12 and C44) and temperature variations of Debye temperature (θD) with parameters determined for both the metals at observed structures. We have computed results of physical properties, but they are not in good agreement with experimental and other theoretical results. Thus, we conclude that the pseudopotential is found to be favorable in extreme environments but not good for theoretical description in phase change and readjustment of parameters is needed. [ABSTRACT FROM AUTHOR]

Many Lattice dynamic models were developed in the past to study the lattice dynamics of metals and their properties. In this present study force constants of Sodium metal have been calculated with the help of De Launay Angular force model. The number of force constants varies with the nature and range of atomic interactions. In the phenomenological theories the force constant of Sodium are evaluated by making use of the experimental data on elastic constants at selected wave vectors. The basic equation of De Launay Angular force model (DAF) relates three elastic constants, force constants as well as two zone boundary frequencies. In the present study, ion-ion interactions of Sodium are considered by neglecting its electron-ion interaction from the proposed relation of DAF model because sodium is the best example of free electron. The force constants of Sodium are calculated here by restricting the range of interaction up to third nearest neighbor. The third angular force constant is considered as neglected because of weaker interaction due to conduction electrons of Sodium. The purpose of this paper is to calculate force constants of Sodium by De Launay Angular Force Model which can be used further in calculation of phonon frequencies of Sodium. [ABSTRACT FROM AUTHOR]

The crystalline structure of bis(4-amino-3,5-dinitropyrazol-1-yl)methane (BDNAPM) was optimized from ambient pressure to 30 GPa using density functional calculations in order to find pressure-induced instabilities. Raman spectra were calculated as a function of pressure using density functional perturbation theory and linear response for lattice dynamics. The zone center (k=0) optical modes provided information about the vibrational modes of the crystal. The calculated spectra were accompanied with high-pressure experimental X-ray diffraction and Raman spectroscopic measurements in the same pressure range. The enthalpy of formation was calculated along with the mass density for simulation of heat of formation and Chapman-Jouguet detonations characteristics. [ABSTRACT FROM AUTHOR]

Due to the combination of superconductivity and type-II Dirac fermions, PdTe2, has acquired noteworthy attraction among the scientific community. The present work reports the structural, phonon, Raman and electronic analysis of two dimensional (2D) PdTe2 transition metal dichalcogenide using first-principles calculations. The calculated lattice constant of 2D PdTe2 is a=4.021Å. The phonon calculation shows the dynamical stability of 2D PdTe2. The calculated Raman spectra show two intense peaks at 127 cm−1 and 147cm−1. Bulk structure of PdTe2 is metallic in nature while our calculated 2D structure of PdTe2 shows semiconducting nature with the narrow indirect band gap of 0.3 eV. Our findings show prospects for its future applications in electronics, optoelectronics and topological superconductivity. [ABSTRACT FROM AUTHOR]

The polycrystalline Sr2IrO4 has been studied using Raman spectroscopy and magnetization. The magnetizationmeasurement confirms canted antiferromagnetic transition below TN= 240 K. Temperature dependent Raman spectroscopic study on Sr2IrO4 has been carried out down to 90 K to investigate the correlation among vibrational and spin degree of freedom. We specifically investigated Ir-O-Ir vibrations (R2 mode) which is related to octahedral tilt as well as exchange interaction. Anomalous hardening of R2 mode below Neel temperature is observed and the deviation of the phonon frequency from the anharmonic behavior is shown to scale with the square of the reduced magnetization. [ABSTRACT FROM AUTHOR]

In this paper, the problem of Rayleigh waves in an incompressible non – local elastic solid under gravity effect is studied. The velocity equation is derived and it is compared with the corresponding equation of the lattice dynamics to seek the variation between reduced frequency and the reduced wave number. This variation is presented graphically and it is observed that frequency is an increasing function of wave number and it decreases for an increase of gravity. [ABSTRACT FROM AUTHOR]

Using second order perturbation theory in the present study, we have investigated lattice dynamics in symmetric directions and second order elastic constants (C11, C12 and C44) for ordered Cu3Au binary alloys. The theoretical results of lattice dynamics and second order elastic constants (SOEC) are in a good agreement with experimental findings and available theoretical results. We conclude that the effective valency determine from first principles method with local pseudopotential do play an important role for theoretical understanding of physical properties of Cu3Au. [ABSTRACT FROM AUTHOR]

Within the framework of an unified ab initio approach the crystal structure, the effect of hydrostatic pressure on the crystal structure, and the phonon spectra of crystals FeBO3 and GaBO3 were investigated. Also, an analysis of the displacement vectors has been obtained from the ab initio calculation, which made it possible to estimate the degree of the ion displacements in each vibrational mode. Calculations were carried out within the framework of MO LCAO approach and the density functional theory, by using PBE0 hybrid functional which takes into account both the local and nonlocal (in the Hartree--Fock formalism) exchange.The calculations were performed with CRYSTAL14 software designed to simulate periodic structures. The results of the performed calculations suggest new features of the title crystals under pressure and new vibrational properties. [ABSTRACT FROM AUTHOR]

In this report, we have investigated the structural and lattice dynamical properties of Half Heusler alloys RuMnX (X=P, As) under the framework of first principles calculations. The structural parameters such as lattice constants have been calculated and found to be in good agreement with the available theoretical results, while bulk modulus and pressure derivative of bulk modulus has been reported for the first time. A linear response approach of density functional perturbation theory has been employed for the calculations of lattice dynamics of these alloys. The calculated phonon dispersion curve (PDC) does not show any imaginary frequency in any symmetric directions, indicating the stability of alloys in the cubic phase. All the phonon frequencies corresponding to acoustical and optical phonon modes have been assigned. Comparison of PDC of both alloys reveal that the phonon gap has been found to be more in RuMnAs than in RuMnP. Lattice dynamical properties for these alloys has been reported for the first time. The phonon density of states for both alloys have also been calculated. Keywords: Half Heusler alloy, Crystal Structure, Lattice Dynamics, Phonons. [ABSTRACT FROM AUTHOR]

As it is well known, a zinc oxide is a unique compound, which is widely used in radio electronics, especially, for photoelectric multiplier manufacture. The ZnO conductivity is provided by presence of defects, which are generally divided into two main groups: native and doped defects. However, the detailed mechanism of electricity flow in the ZnO compounds remains unclear. The process of charge transfer is complex and multifactorial; so, it seems promising to use methods of computer simulation for the structure and electricity characteristics of the ZnO point defects structure. The aim of this work is investigation of the ZnO structure by ab initio and atomistic simulation methods for understanding the conductivity details. Ab initio quantum simulation method is based on a discrete variation and spatial integration algorithms for electronic charge calculation. The ZnO defect structure parameters and the numerical characteristics of ZnO point defects structure are researched by atomistic simulation based on an analytical bond-order formalism implemented in GULP software package for lattice dynamics analytical and numerical computations. The obtained numerical parameters give an opportunity for further reconstruction of the ZnO electronic conductivity. [ABSTRACT FROM AUTHOR]

We present a computational study on phonon thermal transport in zigzag and armchair edge shaped nanoribbons of gold and silver with the aim to investigate the effect of edge and ribbon width on thermal transport. For this purpose, we have preformed lattice dynamics calculations based on force field methods as implemented in GULP code, followed by a Nonequilibrium Green’s Function approach. It is found that the thermal conductance varies linearly with the width of ribbon. At comparable width, nanoribbons of Au shows higher phonon thermal conductance than that of Ag. Moreover, zigzag edged nanoribbons are found to have higher thermal conductance than armchair edged nanoribbons. [ABSTRACT FROM AUTHOR]

The electronic structure, lattice dynamics and superconducting properties of TiFe intermetallic compound are investigated using plane-wave pseudo potential and linear response method based on density functional theory. The ground state properties such as lattice parameter is in good agreement with previously reported results. The positive phonon frequencies reveal the stability of TiFe compound in B2 (CsCl-type) structure. The metallic nature of TiFe confirmed by the electronic band structure as well as phonon dispersion curves. The superconducting behavior is described in terms of Eliashberg spectral function (α ²F(ω)) and electron phonon coupling constant (λ). The calculated value of superconducting transition temperature (Tc) is 1.15 K which shows good agreement with available experimental data. [ABSTRACT FROM AUTHOR]

Boriçi - Creutz fermions, as minimally doubled fermions, are a kind of local lattice fermions which preserve chiral symmetry but break the hyper - cubic symmetry. In our previous works we have shown the effects of this broken symmetry in the light hadrons spectrum, and also have proposed a method of how to restore it partially for BC fermions using the chiral condensate. The methodology proposed seems very effective, with low computational costs and the taken results confirmed the partial restauration of the hyper - cubic symmetry. What we want to test is the effect of this restauration in the light hadrons spectrum. In this work we present some preliminary results of the calculations of the pion mass, in two different lattice directions, using the same conditions in which we have restored the hyper - cubic symmetry. So, we have worked in the quenched approximation, in a background of 100 gauge configurations, β = 6, in a 244 lattice and for the counterterm value of c3 = 0.4. The results show that the pion mass is almost the same in the two different directions, considering the small lattice and statistical errors, a sign that confirm the partial restauration of the hyper - cubic symmetry [ABSTRACT FROM AUTHOR]

In the paper a description of heat transfer in a one-dimensional two-layered metal film is considered. The fuzzy coupled lattice Boltzmann equations for electrons and phonons supplemented by appropriate boundary and initial conditions are applied to analyse the thermal process in a thin metal film. The model with fuzzy values of relaxation times and boundary-initial conditions for gold and titanium is proposed. The problem considered is solved by the fuzzy lattice Boltzmann method using a-cuts and the rules of directed interval arithmetic. The application of a-cuts allows one to avoid complicated arithmetical operations in the fuzzy numbers set. In the final part of the paper an example for a numerical solution is presented. [ABSTRACT FROM AUTHOR]

LiLa9)(SiO4)6)O2) (LLSO) crystals present an interesting host lattice with partially disordered apatite structure. Spectra of photoluminescence (PL) in region of 1.5-5.5 eV, PL excitation spectra (3-6 eV), X-ray excited luminescence and luminescence decay kinetics were measured at room temperature and T= 90 K in LLSO doped with Ce3+ (1%) and Pr3+ (1 %) ions. Interconfigurational d→f transitions are observed in Ce3+ ions replacing La3+ in two cationic sites with different coordination environment. The excited 4fn-15d-states of Ce3+ ions are strongly dependent on local coordination environment. Intraconfigurational f→f transitions in visible (discrete PL spectrum) and interconfigurational d→f transitions in UV region (two broad bands in PL spectrum) are observed in LLSO:Pr3+. The photon cascade emission is not observed in Pr3+ ions, since 1S0 state is above excited 4fn-15d mixed-states zone or overlaps with it. Moreover, apart from RE3+ ions luminescence, low-temperature defect-related luminescence has been observed under UV and X-ray excitation. [ABSTRACT FROM AUTHOR]

We propose a method of applying lattice algebra to the analysis of multivariate time series data. We measured the body motion of a Shorinji-Kempo kata using acceleration sensors at five positions on the body. The proposed analysis was applied to the time series data obtained from the sensors. As a result, a correlation was observed between the skill levels and the number of elements of the lattice generated using the time series data. We observed that highly skilled subjects executed more complex motions; thus, we consider the number of lattice elements as an index of complexity of the space-time pattern. [ABSTRACT FROM AUTHOR]

Fuel cells are devices that allow conversion of the chemical potential of a fuel and oxidant to produce electricity. A key component of a fuel cell is the catalyst layer, which facilitates the electrochemical reaction and where transport of reactants, charge, and byproduct heat and water take place. The structure and morphology of the catalyst layer determine its effectiveness and, in turn, strongly impact the overall performance and cost of a fuel cell. This paper discusses two central issue related to catalyst layers involving two-phase flow: liquid water transport in the catalyst layer during fuel cell operation, and fabrication of the catalyst layer from colloidal inks where a process of particle agglomeration takes place and eventually determines the final catalyst layer structure. Insight into these two issues are obtained using lattice-Botzmann based multi-phase simulations with formulations tailored to deal with features including high density ratio gas-liquid flow in complex porous media, and particle-particle and particle-hydrodynamic interactions. [ABSTRACT FROM AUTHOR]

The paper presents the study on dependence of the kinetic energy per unit length of the dislocation loop, velocity and run on the dislocation density, lattice and impurity friction in nickel, copper, aluminum, and lead. The study is carried out using the mathematical model of dislocation loop expansion dynamics based on the assumption that the dislocation loop expands in a homogeneous isotropic medium, and has the shape of a circle both during the emission by the dislocation source and during its expansion. Computational experiments are carried out by varying the material density from 4·1011 m-2 to 1012 m-2, and the value of the lattice and friction impurity from 0.1 MPa to 2 MPa, with the same value of stress acting on the dislocation source and values of material properties specific to room temperature. Nickel served as an example to exhibit the dynamics of change in dislocation velocity and kinetic energy per unit length of the dislocation at different values of material density and value of lattice and impurity friction for the first and the last dislocation. In conclusion, a comparison of dynamic characteristics of dislocation loops in copper, aluminum, and lead is carried out with similar characteristics for nickel. The obtained data were compared with experimental studies. [ABSTRACT FROM AUTHOR]

The energetics, structures, and properties of lattice defects in semiconductors are discussed on the basis of predictions using first-principles calculations. New insights into the atomistic and electronic structure of point defects are obtained, including significant off-centering of Ti antisite defects and local octahedral rotation around O vacancies in SrTiO3, both of which are accompanied by electron localization. Another example is the formation of a luminous dopantvacancy complex in cubic BN. Band alignment at semiconductor surfaces and heterointerfaces is also discussed, with a focus on approximation dependence. [ABSTRACT FROM AUTHOR]

Transition-metal dichalcogenides like molybdenum disulphide have intrigued intensive interest as twodimensional (2D) materials beyond extensively studied graphene due to their unique electronic and optical properties. Here we report the hydrothermal synthesis of MoS2 nanostructures without the addition of any surfactants. The structural and optical properties of the synthesized samples were characterized by various techniques, including X-ray diffraction (XRD), UV-Vis absorption, photoluminescence (PL), and Raman analysis. XRD and Raman spectroscopic studies confirm the formation of hexagonal phase and well ordered stacking of S-Mo-S layers. The increased lattice parameters of MoS2 samples are due to the stress or strain induced bending and folding of the layers. The synthesized MoS2 nanostructures shows a large optical absorption in 300-700 nm region and strong luminescence at 640 nm. In addition, the optical results demonstrates the quantum confinement in layered d-electron material MoS2 that can lead to engineer its various properties for electronic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Raman and infrared investigations of the recent Aurivillius oxides K0.25Na0.25La0.5Bi2Nb2O9(KNBN-La) and K0.25Na0.25Bi2.5Nb2O9(KNBN-Bi) has been made using normal coordinate analysis in orthorhombic A21am space group. The calculation of zone center phonons incorporates nine stretching and nine bending force constants. The Raman and the infrared frequencies have been assigned and calculated in a very good agreement with the observed frequencies. The potential energy distribution has also been investigated for determining the significance of contribution from each force constant toward the Raman and the infrared wavenumbers. [ABSTRACT FROM AUTHOR]

Growth of ultrathin Co layers on close-packed Ag(111)were investigated by means of Low Energy Electron Diffraction (LEED), X-ray Photoelectron Spectroscopy (XPS) and Angle-resolved Photoemission Spectroscopy(ARPES) techniques. The close-packed hexagonal face of Co(0001), exhibits a lattice misfit about 13% with Ag(111) surface which manipulates the growth to be incommensurate up to a certain thickness. The strain field causes aperiodic height undulation in the sub-angstrom regime of the film which was confirmed by p(1×1) LEED pattern along with a 6-fold moiré reconstruction pattern in the lower film thickness (up to ∼2ML). The evolution of the LEED pattern was studied with increasing film coverage. Lattice strain was measured with respect to the relative positions of these double spots as a functionof film thickness. Almost a constant strain (∼13%) in the full range of film thickness explains the moiré pattern formation in order to stabilize the incommensurate growth. For higher film coverages, an epitaxial well-ordered commensurate growth was observed. Core level and valance band electronic structures of these films were studied by XPS and ARPES techniques. [ABSTRACT FROM AUTHOR]

Vibrational studies on Raman and infrared active phonons in orthorhombic phase for Mg2SiO4 have been made by applying a short range force constant model. The lattice dynamical calculations were carried out by Wilson's GF matrix method by normal coordinate analysis of Mg2SiO4 having space group Pbnm in orthorhombic phase. The calculations have been made with fifteen stretching and eleven bending force constants. The calculated values of Raman and infrared phonons are in good agreement with the experimental results. The contribution of each force constant towards the zone centre phonons has been determined in terms of potential energy distribution. [ABSTRACT FROM AUTHOR]

Raman and infrared investigations of the recent Aurivillius oxides K0.25Na0.25La0.5Bi2Nb2O9(KNBN-La) and K0.25Na0.25Bi2.5Nb2O9(KNBN-Bi) has been made using normal coordinate analysis in orthorhombic A21am space group. The calculation of zone center phonons incorporates nine stretching and nine bending force constants. The Raman and the infrared frequencies have been assigned and calculated in a very good agreement with the observed frequencies. The potential energy distribution has also been investigated for determining the significance of contribution from each force constant toward the Raman and the infrared wavenumbers. [ABSTRACT FROM AUTHOR]

Vibrational studies on Raman and infrared active phonons in orthorhombic phase for Mg2SiO4 have been made by applying a short range force constant model. The lattice dynamical calculations were carried out by Wilson's GF matrix method by normal coordinate analysis of Mg2SiO4 having space group Pbnm in orthorhombic phase. The calculations have been made with fifteen stretching and eleven bending force constants. The calculated values of Raman and infrared phonons are in good agreement with the experimental results. The contribution of each force constant towards the zone centre phonons has been determined in terms of potential energy distribution. [ABSTRACT FROM AUTHOR]

Spectra of excitonic excitations in a high-symmetry 2D molecular lattice with two different entities-donors and acceptors have been studied. We use the geometry of two hexagonal sub-lattices in graphene created by donors and acceptors, respectively, and investigate both Frenkel excitons (FEs) and charge-transfer excitons (CTEs) along with their coupling and manifestation in the linear absorption spectra. Vibronic spectra that consist of excitons and one-mode intramolecular vibrations of the donor or acceptor molecules are explored both analytically and numerically. Our calculations model the excitonic density of state and the linear absorption spectra in excitonic and vibronic regimes for two polarization of light, notably in the lattice plane and perpendicular to it. Lineshapes of the absorption depend upon the FE-CTEs-phonon coupling and exhibit bound and unbound exciton-phonon states in one-phonon and two-phonon vibronic spectra. [ABSTRACT FROM AUTHOR]

We report recent results of a non-perturbative determination of the static heavy-quark potential in quenched and dynamical lattice QCD at finite temperature. The real and imaginary part of this complex quantity are extracted from the spectral function of Wilson line correlators in Coulomb gauge. To obtain spectral information from Euclidean time numerical data, our study relies on a novel Bayesian prescription that differs from the Maximum Entropy Method.We perform simulations on quenched 323 ×Nτ (β = 7.0,ξ = 3.5) lattices with Nτ = 24, . . . , 96, which cover 839MeV ≥ T ≥ 210MeV. To investigate the potential in a quark-gluon plasma with light u,d and s quarks we utilize Nf = 2+1 ASQTAD lattices with ml = ms=20 by the HotQCD collaboration, giving access to temperatures between 286MeV ≥ T ≥ 148MeV. The real part of the potential exhibits a clean transition from a linear, confining behavior in the hadronic phase to a Debye screened form above deconfinement. Interestingly its values lie close to the color singlet free energies in Coulomb gauge at all temperatures. We estimate the imaginary part on quenched lattices and find that it is of the same order of magnitude as in hard-thermal loop perturbation theory. From among all the systematic checks carried out in our study, we discuss explicitly the dependence of the result on the default model and the number of datapoints. [ABSTRACT FROM AUTHOR]

The problem of self-consistent estimates of the deconfinement temperature Tc in the framework of the bottomup holographic approach to QCD is observed. It is shown that the standard soft wall model gives Tc around 260 MeV for planar gluodynamics in a good agreement with the lattice data. The extensions of soft wall model adjusted for descriptions of realistic meson spectra result in a broad range of predictions. This variability is related to a poor experimental information on the radially excited mesons. [ABSTRACT FROM AUTHOR]

We consider a QCD chiral symmetry breaking model where the gap equation contains an effective confining propagator and a dressed gluon propagator with a dynamically generated mass. This model is able to explain the ratios between the chiral transition and deconfinement temperatures in the case of fundamental and adjoint quarks. It also predicts the recovery of the chiral symmetry for a large number of quarks (nf ≈ 11-13) in agreement with lattice data. [ABSTRACT FROM AUTHOR]

The dissociation of heavy quarkonium seen in heavy-ion collisions is a phenomena that allows to extract information of the produced thermal medium. This was believed to be due to the screening of the static potential but recently perturbative computations and some lattice studies have pointed out the possibility of having an imaginary part of the potential that would also contribute to dissociation. In recent years a program to study heavy quarkonium with the use of non-relativistic effective field theories (EFTs) has been started, this allows to make the computations in a more systematic way by defining a more suitable power counting and making it more difficult to miss necessary resummations. However until now these studies have been done assuming thermal equilibrium. In this work we will discuss what happens in the EFT formalism when heavy quarkonium is in a medium that is not in thermal equilibrium and what is the expected suppression when a medium with a time dependent effective temperature that follows Bjorken evolution is considered. This will be done adapting previous results from different temperature regimes. [ABSTRACT FROM AUTHOR]

The phase diagram of two-color QCD with a chiral chemical potential is studied on the lattice. The focus is on the confinement/deconfinement phase transition and the breaking/restoration of chiral symmetry. The simulations are carried out with dynamical staggered fermions without rooting. The dependence of the Polyakov loop, the chiral condensate and the corresponding susceptibilities on the chiral chemical potential and the temperature are presented. [ABSTRACT FROM AUTHOR]

I report on progress by the HPQCD Collaboration using radiatively-improved lattice NonRelativistic QCD and relativistic HISQ valence quarks on ensembles of gluon field configurations, generated by the MILC collaboration that now include u, d, s and c HISQ quarks in the sea, with the u/d quark masses going down to their physical value. I describe the background field approach for determining the one-loop radiative improvement to coefficients in the NRQCD action, and I present the most accurate results yet for a range of quantities, including: the hyperfine splittings Mr -Mηb and MB*q -MBq ; fB, fBs and the leptonic decay constants fr(i); B-meson masses mBq for q = u/d, s, c; B - B mixing; the b-quark mass mb; and the lattice calculation for the rare decays B0 → K*0μ+μ- and Bs →ϕμ+μ-. I briefly discuss future prospects. [ABSTRACT FROM AUTHOR]

We discuss the lattice QCD simulations that search for the Z+c with the unconventional quark content ccdu in the channel IG(JPC) = 1+(1+-). The major challenge is due to the two-meson states J/Ψπ, Ψ2Sπ, Ψ1Dπ, DD*, D*D*, ηcρ that are also inevitably present in this channel. The available lattice simulations find expected two-meson eigenstates, but no additional eigenstate as a candidate for Z+c. This is in a striking contrast to the lattice results in the flavour non-exotic channels, where additional states are found in relation to most of the known resonances and bound states. [ABSTRACT FROM AUTHOR]

In order to investigate quark confinement, we give a new reformulation of the SU(N) Yang-Mills theory on a lattice and present the results of the numerical simulations of the SU(3) Yang-Mills theory on a lattice. The numerical simulations include the derivation of the linear potential for static interquark potential, i.e., non-vanishing string tension, in which the "Abelian" dominance and magnetic monopole dominance are established, confirmation of the dual Meissner effect by measuring the chromoelectric flux tube between quark-antiquark pair, the induced magnetic-monopole current, and the type of dual superconductivity, etc. [ABSTRACT FROM AUTHOR]

Recent progress in lattice QCD calculations of nucleon structure will be presented. Calculations of nucleon matrix elements and form factors have long been difficult to reconcile with experiment, but with advances in both methodology and computing resources, this situation is improving. Some calculations have produced agreement with experiment for key observables such as the axial charge and electromagnetic form factors, and the improved understanding of systematic errors will help to increase confidence in predictions of unmeasured quantities. The long-omitted disconnected contributions are now seeing considerable attention and some recent calculations of them will be discussed. [ABSTRACT FROM AUTHOR]

We discuss a generalization of the Lüscher approach to the calculation of the matrix elements of the unstable states. A theoretical framework for the lattice extraction of the ΔNγ* transition form factors is formulated. The procedure to measure the form factors at the resonance pole is given. The current theoretical progress on the B→K*γ* decays is briefly summarized. [ABSTRACT FROM AUTHOR]

Electromagnetic polarizabilities are important parameters for understanding the interaction between photons and hadrons. For pions these quantities are poorly constrained experimentally since they can only be measured indirectly. New experiments at CERN and Jefferson Lab are planned that will measure the polarizabilities more precisely. Lattice QCD can be used to compute these quantities directly in terms of quark and gluons degrees of freedom, using the background field method. We present results for the electric polarizability for two different quark masses, light enough to connect to chiral perturbation theory. These are currently the lightest quark masses used in polarizability studies. [ABSTRACT FROM AUTHOR]

We study the operator product expansion of the plaquette (gluon condensate) and the self-energy of an infinitely heavy quark. We first compute their perturbative expansions to order α35 and α20, respectively, in the lattice scheme. In both cases we reach the asymptotic regime where the renormalon behavior sets in. Subtracting the perturbative series, we obtain the leading non-perturbative corrections of their respective operator product expansions. In the first case we obtain the gluon condensate and in the second the binding energy of the heavy quark in the infinite mass limit. The results are fully consistent with the expectations from renormalons and the operator product expansion. [ABSTRACT FROM AUTHOR]

The Polyakov loop and the Dirac modes are connected via a simple analytical relation on the temporally odd-number lattice, where the temporal lattice size is odd with the normal (nontwisted) periodic boundary condition. Using this relation, we investigate the relation between quark confinement and chiral symmetry breaking in QCD. In this paper, we discuss the properties of this analytical relation and numerically investigate each Dirac-mode contribution to the Polyakov loop in both confinement and deconfinement phases at the quenched level. This relation indicates that low-lying Dirac modes have little contribution to the Polyakov loop, and we numerically confirmed this fact. From our analysis, it is suggested that there is no direct one-to-one corresponding between quark confinement and chiral symmetry breaking in QCD. Also, in the confinement phase, we numerically find that there is a new "positive/negative symmetry" in the Dirac-mode matrix elements of link-variable operator which appear in the relation and the Polyakov loop becomes zero because of this symmetry. In the deconfinement phase, this symmetry is broken and the Polyakov loop is non-zero. [ABSTRACT FROM AUTHOR]

In a string picture, the nucleon is conjectured as consisting of a Y-shaped gluonic string ended by constituent quarks. In this proceeding, we summarize our results on revealing the signature of the confining Y-bosonic string in the gluonic profile due to a system of three static quarks on the lattice at finite temperature. The analysis of the action density unveils a background of a filled-Δ distribution. However, we found that these Δ-shaped profiles are comprised of three Yshaped Gaussian-like flux tubes. The length of the revealed Y-string-like distribution is maximum near the deconfinement point and approaches the geometrical minimal near the end of the QCD plateau. The action density width profile returns good fits to a baryonic string model for the junction fluctuations at large quark source separation. [ABSTRACT FROM AUTHOR]

We summarise reeent progress in simulating QCD at nonzero baryon density using eomplex Langevin dynamies. After a brief outline of the main idea, we diseuss gauge eooling as a means to eontrol the evolution. Subsequently we present a status report for heavy dense QCD and its phase strueture, full QCD with staggered quarks, and full QCD with Wilson quarks, both direetly and using the hopping parameter expansion to all orders. [ABSTRACT FROM AUTHOR]

An investigation of Raman and the infrared wavenumbers has been made by using normal coordinate analysis in TmPO4 crystal having space group 141/a and symmetry C4h6. The zone center phonons has been calculated by using four stretching and five bending force constants. The present calculations are in very good agreement with the available experimental results. The potential energy distribution (PED) has also been investigated for determining the significance of contribution from each force constant toward the Raman and the infrared wavenumbers. [ABSTRACT FROM AUTHOR]