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In this study, La0.5Ba0.5MnO3 has been synthesized by hydrothermal method. Crystal structure and morphology are determined by x-ray diffraction and scanning electron microscopy. It is observed that Ba-doped LaMnO3 (LMO) has the same cubic crystal structure as the host material with space group $\text {Pm}\bar {3}\mathrm {m}$ . Half of the La atoms are replaced by Ba in the composition. Further, the electronic and magnetic structures are investigated by solving the Kohn-Sham equation with the full-potential linearized augmented plane wave method (FP-LAPW), with GGA+U approximation for exchange and correlation, for Ba concentration from 12.5 to 87.5%. The system is half-metallic ferromagnetic (FM) up to 55% and then converts into anti-ferromagnetic (AFM). This happens due to the onset of super exchange on increasing Ba concentrations. It is suggested that Ba-doped LMO is the best material for the fabrication of an exchange-biased spin valve. The spacer material can be any non-magnetic cubic perovskite such as BaTiO3 while the FM and AFM layers can be made of Ba-doped LMO with different concentrations of Ba.

The energy states of the bound electrons in high energy density systems (HEDS) are significantly affected due to the electric field of the neighboring ions. Due to this effect bound electrons require less energy to get themselves free and move into the continuum. This phenomenon of reduction in potential is termed as ionization potential depression (IPD) or the continuum lowering (CL). The foremost parameter to depict this change is the average charge state, therefore accurate modeling for CL is imperative in modeling atomic data for computation of radiative and thermodynamic properties of HEDS. In this paper, we present an improved model of CL in the screened hydrogenic model with l-splitting (SHML) proposed by G. Faussurier and C. Blancard, P. Renaudin [High Energy Density Physics 4 (2008) 114] and its effect on average charge state. We propose the level charge dependent calculation of CL potential energy and inclusion of exchange and correlation energy in SHML. By doing this, we made our model more relevant to HEDS and free from CL empirical parameter to the plasma environment. We have implemented both original and modified model of SHML in our code named OPASH and benchmark our results with experiments and other state-of-the-art simulation codes. We compared our results of average charge state for Carbon, Beryllium, Aluminum, Iron and Germanium against published literature and found a very reasonable agreement between them.

The electronic structure and magnetic properties of Mn doped zinc blende cadmium sulfide Cd1-xMnxS (x = 6.25 %) have been studied using spin-polarized density functional theory within the framework of Generalized Gradient Approximation (GGA), its further corrections including Hubbard U interactions (GGA + U) and a model for exchange and correlation potential Tran Blaha modified Becke-Johnson (TB-mBJ). Ferromagnetic interactions have been observed between Mn atoms via S atom due to strong p-d hybridization. The magnetic moments on Mn and its neighboring atoms have also been studied in detail using different charge analysis techniques. It has been observed that p-d hybridization reduced the value of local magnetic moment of Mn in comparison to its free space charge value and produced small local magnetic moments on the nonmagnetic S and Cd host sites. The magnetocrystalline anisotropy in [1 0 0] and [1 1 1] directions as well as exchange splitting parameters Noα and Noβ have been analyzed to confirm that ferromagnetism exists. We conclude that the ferromagnetic phase in Mn-doped CdS is not stable in “near” configuration but it is stable for “far” configuration. Mn doped CdS is a p-type semiconductor and the d-states at the top of the valence band edge give a very useful material for photoluminescence and magneto-optical devices.

High pressure investigations of matter involve the study of strong shock wave dynamics within the materials which gives rise to many thermal effects leading to dissociation of molecules, ionization of atoms, and radiation emission, etc. The response of materials experiencing a strong shock can be determined by its shock Hugoniot calculations which are frequently applied in numerical and experimental studies in inertial confinement fusion, laboratory astrophysical plasma, etc. These studies involve high energy density plasmas in which the radiation plays an important role in determining the energy deposition and maximum compressibility achieved by the shock within material. In this study, we present an investigation for the effect of radiation pressure on the maximum compressibility of the material using shock Hugoniot calculations. In shock Hugoniot calculations, an equation of state (EOS) is developed in which electronic contributions for EOS calculations are taken from an improved screened hydrogenic model with –l splitting (I-SHML) [High Energy Density Physics (2018) 26 48] under local thermodynamic equilibrium (LTE) conditions. The thermal ionic part calculations are adopted from the state of the art Cowan model while the cold ionic contributions are adopted from the scaled binding energy model. The Shock Hugoniot calculations are carried out for sodium and iron plasmas and our calculated results show excellent agreement with published results obtained by using either sophisticated self-consistent models or the first principle study.

Ion population fraction (IPF) calculations are very important to understand the radiative spectrum emitted from the hot dense matter. IPF calculations require detailed knowledge of all the ions and correlation interactions between the electrons of an ion which are present in a plasma environment. The average atom models, e.g., screened hydrogenic model with l-splitting (SHML), now have the capabilities for such calculations and are becoming more popular for in line plasma calculations. In our previous work [Ali A, Shabbir Naz G, Shahzad M S, Kouser R, Rehman A and Nasim M H 2018 High Energy Density Phys.26 48], we have improved the continuum lowering model and included the exchange and correlation effects in SHML. This study presents the calculation of IPF using classical theory of fluctuation for our improved screened hydrogenic model with l-splitting (I-SHML) under local thermodynamic equilibrium conditions for iron and aluminum plasma over a wide range of densities and temperatures. We have compared our results with other models and have found a very good agreement among them.

In this article, we investigate the effects of foam target composition and laser parameters on deuterium ion energy spectrawith particle-in-cell simulations. We findthat localized electrostatic fieldswith multi peaksaroundthe surfaces of lamellarlayersinsidefoamtargetareinduced.Thesefieldsacceleratedeuteriumionsfromthinfoamlayersbyrestrictingtheflowofhot electrons. This mechanism of ion acceleration called as bulk ion acceleration generates large number of high energydeuteriumions. Deuteronsinside foam target are accelerated upto 126 MeVin case ofobliqueoptimal angle of308 whereit is much greater than the normal laser incidence energy of 88 MeV.Keywords: Bulk ion acceleration; Deuteron acceleration; Foam target; Intense laser; Laser-produced plasma INTRODUCTIONWith the achievement of laser intensities well above10 18 Wcm 22 , fast moving ions with kinetic energiesapproaching several tens of MeV have been observed(Clark et al., 2000; Snavely et al., 2000; Hatchett et al.,2000). The striking features of laser-produced ions havealready actuated a broad variety of studies concerning theunderlying physical processes and possible applicationslike proton radiography (Mackinnon et al., 2006), isochoricheating of matter (Patel et al., 2003), and cancer therapy(Malka et al., 2009). The fast ignition concept pertainingto inertial confinement fusion (ICF) also enhances interestsin laser-driven ion acceleration (Tabak et al., 1994; Rothet al., 2001; Eliezer et al., 2007; Hora, 2007; Winterberg,2008; Naumova et al., 2009).In the interaction of femtosecond laser pulses with solidselectron beams are generated and accelerated to highly rela-tivistic energies. The laser pondermotive force pushes thesehot electrons out of the laser focus. The expelled electronsformanelectricfieldattargetfrontsurfaceduetochargesep-aration of electrons and ions. Ions produced at the frontsurface are accelerated inside the target. This mechanism ofion acceleration is called front side acceleration. Fastelectrons also propagate away from laser irradiated surfacetoward the vacuum forming an electrostatic sheath whichresults in ion acceleration in front of the target (Temporalet al., 2002). A significant number of laser-driven hot elec-trons propagate through the target and emerge from targetrear surface. Space-charge separation at target rear surfaceforms an electrostatic filed sufficient for ionizing atoms andcauses strong acceleration of ions along the target normal.This mechanism of ion acceleration is called TargetNormal Sheath Acceleration (TNSA) (Wilks et al., 2001;Brambrink et al., 2006; Limpouch et al., 2008). At moderatelaser intensities, a collisionless electrostatic shock wave isformed in thin foils, which can accelerate ions to highenergy (Chen et al., 2007; Liu et al., 2009). This mechanismof ion acceleration exists widely in space and astrophysicalplasmas. At high laser intensities ( 10

The objective of the present paper is to study the dissipative trapped electron modes (DTEM) in a stellarator configuration. A perturbative-iterative process is used to study the non-adiabatic response of the electrons in the dissipative regimes on the drift wave instability. A ballooning mode formalism is used to drive the drift eigenvalue equation for adiabatic electron which is solved numerically. The eigenmodes are marginally stable. The non-adiabatic response of the electrons is calculated perturbatively which is used to re-solve the eigenvalue equation. The process is iterated until electrons response converges. The effects of different parameters such as ηe, the ballooning angle θk, normalised density scale length n, radial label s, and χ are studied. The mode localisation is correlated with the geometrical properties of the magnetic field. It is found that the wave functions of the most unstable modes are highly localised in a single helical ripple with the possibility of a variety of both helical and toroidal trapping. It is further fond that a perturbative calculations of the growthrate generally is not reliable and can give substantially lower or higher growthrate than the iterative method.

Modern stellarators are designed with neoclassical transport in mind, potentially leading to anomalous transport originating from drift wave turbulence as the primary cause of energy and particle losses. It is therefore of interest to consider the influence of details of geometry on drift wave stability. In this paper the eigenvalue drift wave equation is therefore solved numerically in fully three-dimensional stellarator geometries using the ballooning mode formalism. The correlation between the details of the configurations such as local magnetic shear (LMS), normal curvature, geodesic curvature and magnetic field strength and the drift wave spectrum is discussed for two different stellarator configurations. A detailed discussion of the localization of the most unstable modes is presented and analysed. It is found that the most unstable modes are localized where the stabilizing effect of integrated LMS is minimum or where the coupling between the integrated LMS and geodesic curvature is strong. Since the more the modes are localized the stronger they will be influenced by the local geometrical effects, the most unstable modes are also highly localized.

The expressions for the Debye and the wake potential are derived by incorporating dust-charge fluctuations of a single projectile, as well as of an array of dust grain projectiles, propagating through a partially ionized dusty plasma with a constant velocity. Numerically, the effects of the dust-charge fluctuations and the dust–neutral collisions on the electrostatic potential for a single, three, six and ten projectiles are examined. The dust-charge relaxation rate modifies the shape of the Debye as well as the wake potential. For smaller values of the relaxation rates a potential well is formed instead of Debye potential.

The dielectric response function for modified dust acoustic waves is studied, incorporating the dipole moment and moment of inertia of finite sized elongated dust grains. Using this dielectric constant, generalized expressions for the Debye potential and for the wake potential are obtained due to a cluster of N2 dust grain projectiles moving with a constant velocity along the z-axis through a multi-component dusty plasma. For illustration, numerical results due to single, three, and six projectiles are presented with and without a dipole effect. A negative wake potential is observed behind each projectile in different geometeries.

The shielded potential and the energy loss of N2 projectiles propagating through a multicomponent dusty plasma are studied. Analytically general expressions have been obtained for the potential and for the energy loss, taking into account the two-body correlation effects. However, numerical calculations have been performed for one, three, and six projectiles, incorporating interference between two consecutive projectiles. It is found that the correlation effect causes distortion in the potential profile depending upon the separation between the two projectiles. The distortion becomes pronounced for separation smaller than the Debye length.

Wide band gap magnetic semiconductors made of lanthanide compounds have a wide range of applications in opto-magneto-electronic industry and electro (photo) luminescence devices. We have carried out a systematic study of electronic, magnetic and optical properties of rare earth potassium sulfides KMS2 (M = Nd, Ho, Er, and Lu) using density functional theory (DFT) with full potential linearized augmented plane wave method (FP-LAPW). Different exchange and correlation approximations are employed such as generalized gradient approximation (GGA), GGA + U and TB-mBJ. It is inferred that the GGA + U approach correctly predicts the localized behavior of 4f electrons in lanthanide atoms for the calculation of band gaps, electronic, magnetic and optical properties. All compounds are stable in ferromagnetic phase except KLuS2, while KLuS2 is a non-magnetic semiconductor because there is no unpaired f-electron. Band gaps of KMS2 are estimated and these materials are found to be wide band gap semiconductors. These materials absorb mainly ultraviolet (UV) radiations, which make them good photoluminescent materials with a strong dependence on the direction of the polarization of incident photons.

We present the preliminary results of our code OPAQS (opacity calculation using quantum statistical model) that is based on the self consistent Hartree–Fock–Slater model for the average atom. The code is capable of performing robust calculations of average charge state, frequency-dependent and mean opacities. The accuracy of the atomic model is verified by comparing the calculations of average charge state with various published results. The monochromatic opacities for iron computed at different sets of temperatures and densities are compared with LEDCOP. The Rosseland and Planck opacities for iron and aluminum are validated with some state-of-the-art codes. The results are in good agreement with the published data.

The energy loss of a test charge in an unmagnetized dusty plasma is estimated for different dust parameters (such as dust charge state, dust number density, dust charge fluctuations and dust-neutral collisions) using Krook and BGK-type collisional models. We find that the higher the dust-charge-state the more pronounced is the wake-fleld (which extends up to several Debye lengths). The variation of the dust number density shows a similar behavior. For large dust-neutral collisions a weakly damped large amplitude wake-field is observed which jumps ahead of the test charge position for higher collision frequencies. The dust neutral collisions are also found to enhance the energy loss for test charge velocities greater than the dust acoustic speeds in contrast with the dust charge fluctuations which enhances the energy loss only for test charge velocities smaller than the dust acoustic speeds.

The energy loss of a test charge particle in an unmagnetized dusty plasma is estimated, by incorporating the dust–neutral collisions. A slowly damping large amplitude wake field is observed which moves ahead of the test charge position for large dust–neutral collision frequencies. A critical test charge velocity is determined for a particular dust–neutral collision frequency below which the test charge gains energy instead of losing. The collisions enhance the energy loss only for the test charge velocities greater than the dust acoustic speed.

The energy loss of a test charge in dusty plasma with dust charge fluctuations has been calculated both analytically (within the frame work of dielectric theory) as well as numerically. The dust charge relaxation rate is found to have a significant effect on the total energy loss of a test charge which is the sum of collective response of the plasma and individual particle interaction. It is shown that the dust charge fluctuation enhances the energy loss due to the collective response of the plasma as well as the individual particle contributions. Further, the charge fluctuation converts the static Coulomb potential to a potential well for slow charge relaxation rates and a small test charge velocity. The test charge therefore gains energy instead of loosing. On the other hand for the large test charge velocity and fast charge relaxation rate, a shielded Debye Huckel type potential is formed and consequently the energy loss is enhanced. These results are useful for understanding coagulation of dust grains in space and laboratory plasmas.

The energy loss of a test charged particulate in an unmagnetized dusty plasma is calculated by employing the dusty dielectric response function which accounts for the dust charge fluctuation. It is found that the dust charge fluctuation introduces a new contribution to the energy loss, which enhances it for fast charge relaxation rates and reduces it for slow rates. In the energy loss curves drawn against the test charge velocity, some peaks are observed. These peaks diminish for large charge relaxation rates. Possible explanation for these peaks is also discussed. These results may be useful for understanding coagulation of dust grains in space and laboratory plasmas and for transport of dust particulates in the planetary rings.

The analytical and numerical results for the slowing down of two heavy projectile ions passing through a multicomponent dusty plasma are presented. Within the linear dielectric approach, the electrostatic potential and the stopping power of the two projectiles are computed for different values of KD (the normalized effective wave number) and R (the separation between the two projectiles) retaining two-ion-correlation effects. The enhancement in the energy loss is observed, and it is compared with that of a single ion projectile case. These results are useful to explain the crystallization of dust grains in astrophysical and laboratory plasmas.

The imploding plasma column of a gas-puff Ζ-pinch has been used to compress the target-gas-embedded axial magnetic field in the presence of plasma pressure. The dynamics of a two-gas gas-puff Ζ-θ pinch is studied with different forms of applied current profiles. We find that the inclusion of a kinetic pressure term introduces the usual β–term, which delays and reduces the maximum compression. On the other hand, for fixed β, compression at an earlier time can be achieved for a large density ratio of the test to the driver gas at the interface position. For the pressure-free case, our earlier results are completely recovered.

An expression for two-gas gas-puff Z-θ pinch compression is derived and the dynamic behavior of the implosion is investigated. It is observed that the compression and the azimuthal magnetic field strengths are critically dependent on the target to driver mass density ratio and on the driver gas shell thickness.

We present the fine-structure energy levels, wavelengths, oscillator strengths, transition energies, and transition rates of optically allowed inner-shell transitions of Ne-, Ni-, and Cu-like uranium ions by using the multiconfiguration Dirac–Fock method with the fully relativistic GRASP2 code (partly improved by us). In order to compare these results, we have performed other independent calculations with a fully relativistic Flexible Atomic Code (FAC). We have determined extensive configuration interaction wavefunctions to calculate the level energies of the inner-shell excited states of these three uranium ionic states. Overall, our calculated energy levels, wavelengths, transition rates, and oscillator strengths within the levels of selected configurations show better agreement with the available experimental and other theoretical results. Furthermore, we report radiative lifetimes of all the excited states of these three uranium ions. We also present many unpublished data about energy values, wavelengths, transitions rates, and oscillator strengths for inner-shell transitions. We believe that our calculated inner shell transition energies are of interest for the analysis of uranium x-ray spectra.

We present calculations of atomic radiative data for 89 fine-structure levels generated from 15 configurations (1s22s22p6, 2s22p5nl, 2s2p6nl, n = 3, 4) of the Ne-like Au ion. Transition energies, oscillator strengths and transition rates for transitions among the levels are calculated using two independent fully relativistic atomic codes GRASP2 (partly improved by us) and FAC. Additionally, lifetimes of all 89 levels are reported in this paper. We make a detailed comparison of our results with those of other numerical methods and experiments to assess the accuracy of our results. Our results are in good agreement with the recent experiment performed on the Livermore SuperEBIT machine.

Expressions for the electrostatic potential and the energy loss are derived for a variety of arrays of dust grain projectiles, arranged at different orientations and separations and moving with a constant velocity along the z axis in an unmagnetized collisionless dusty plasma, using linear dielectric theory. By employing the dielectric constant of dust acoustic wave, the Debye and wake potentials are calculated for the projectiles. It is found that a projectile moving with high speed forms a negative wake behind and a shock in front of it. Further, for particular values of interspacing, the three different assemblies exhibit almost similar behavior of the energy loss and thus permit the possibility of all of them to move in unison to establish a dynamical equilibrium in a hexagonal geometry.

Generalized expressions for the Debye potential and the wake field potential are derived due to an axial propagation of dust grain projectiles. The dust grain projectiles are assumed to lie on sets of concentric circles propagating through the dusty plasma with a constant velocity along the z axis. Each circle carries N number of dust grain projectiles having radius rl and angular position (2πm)∕N. A couple of specific cases of electrostatic potential due to four and eight projectiles are studied in some detail both analytically and numerically.

The wake-field excited by a test charge moving through a multicomponent dusty plasma is calculated by using the fluid as well as the Vlasov–Poisson model. It is shown that the ion-wake field may be oscillatory (Vt CDA), depending upon the test charge velocity Vt relative to the dust acoustic speed CDA. Numerical results for the wake-field are presented for different test charge velocities. The work has relevance in space and astrophysical plasmas.