Energy levels and spectral lines of Ne VII

All experimental data on Ne VII, including previously unpublished beam-foil spectroscopy data, have been compiled and critically evaluated. More than a hundred spectral lines have been newly identified. For 40 transitions, the previous identifications have been revised. These revisions resolved all existing contradictions between previously published interpretations of the spectrum. An optimized level scheme has been derived from the total list of observed lines. About a hundred new energy levels have been found, including several highly excited hydrogenic levels. Based on these newly determined levels, as well as on the analysis of theoretical data, the ionization potential has been newly determined with improved confidence. Electronic supplementary material Online Material     

The wavefunction envelope in one-dimensional random potentials

We propose a formalism for the study of mean resistance of a one dimensional chain of random potentials. We obtain the resistance as a function of the length of the chain. In the asymptotic limit, this is related to the wavefunction envelope. The formalism demands loss of translational symmetry, but is general enough to include potentials with spatial correlations which are not long ranged and also those whose randomness is inhomogeneous.     

Semiclassical approximation for relativistic potentials

We consider the application of semiclassical approximation to relativistic potentials for massless particles where the kinetic energy is a nontrivial, nonlocal operator. Quantization rules are derived for an arbitrary confining potential and compared to some exact results forS-waves. These results admit of a partial generalization to smalll values.     

Effect of quantization and positron concentration on shielding potentials in electron-positron-ion plasma

The kinetic theory of plasma has been employed to compute the test-charge potential distributions accounting for quantization effects in magnetized electron-positron-ion (EPI) plasmas. In this regard, the degenerate positrons and electrons are assumed to follow the Fermi-Dirac distribution, while inertial ions are modelled by Maxwellian velocity distribution. By solving the Fourier-transformed Vlasov–Poisson equations, a modified dielectric function and electrostatic potential is obtained. By imposing various constraints on the test-charge speed, the potential profile has been analysed in terms of Debye–Hückel (DH), far-field (FF), and wake-field (WF) potentials. It has been found that the amplitude of DH and FF potentials increases by the inclusion of quantization effects, and it becomes the opposite for the WF potential profile. Furthermore, the variation of positron concentration significantly affects the DH, FF, and WF potentials. The present findings are important to understand the shielding phenomenon in degenerate multi-species plasmas.     

Calculations of dynamic multipolar polarizabilities of the Cd clock transition levels

The pursuit of a systematic frequency uncertainty beyond 10^-18 clock has triggered a multitude of investigations on the multipolar and higher-order lattice light shifts. The Cd atom has been proposed as a new candidate for the development of a lattice clock because of its smaller blackbody radiation shift at room temperature. Here, we apply an improved combined method of the Dirac-Fock plus core polarization and relativistic configuration interaction methods to calculate the dynamic multipolar polarizabilities of the Cd clock states. The effects of the high-order core-polarization potentials on the energies, reduced matrix elements, and multipolar polarizabilities have been evaluated systematically. The detailed comparison with available literature demonstrates that taking into account of the high-order core-polarization potentials is a simple and effective approach to improve the results of atomic properties for heavy atoms.     

Adaptive‐numerical‐bias metadynamics

A metadynamics scheme is presented in which the free energy surface is filled with progressively adding adaptive biasing potentials, obtained from the accumulated probability distribution of the collective variables. Instead of adding Gaussians with assigned height and width in conventional metadynamics method, here we add a more realistic adaptive biasing potential to the Hamiltonian of the system. The shape of the adaptive biasing potential is adjusted on the fly by sampling over the visited states. As the top of the barrier is approached, the biasing potentials become wider. This decreases the problem of trapping the system in the niches, introduced by the addition of Gaussians of fixed height in metadynamics. Our results for the free energy profiles of three test systems show that this method is more accurate and converges more quickly than the conventional metadynamics, and is quite comparable (in accuracy and convergence rate) with the well‐tempered metadynamics method. © 2017 Wiley Periodicals, Inc.     

Rolling of a Rigid Cylinder over a Half-Plane with Initial Stresses (Harmonic and Bartenev–Khazanovich Potentials)

An asymmetric quasistationary problem for a prestressed half-plane with harmonic and Bartenev–Khazanovich potentials is solved based of the linearized theory of elasticity. The Mehler–Fock integral transform is used to solve the differential equations that describe the stress–strain state of the half-plane. The dependences of the normal and tangential stresses and stress intensity factors on the elongation are plotted     

ChemInform Abstract: Evaluation of Tavorite‐Structured Cathode Materials for Lithium‐Ion Batteries Using High‐Throughput Computing.

Tavorite‐structured oxyphosphates, fluorophosphates, oxysulfates, and fluorosulfates are evaluated for use as cathode materials in lithium ion batteries and activation energies for lithium diffusion through LiVO(PO₄), LiV(PO₄)F, and LiFe(SO₄)F are calculated.     

Calculations of D‐wave bound states and resonance states of the screened helium atom using correlated exponential wave functions

We have investigated the effects of screened Coulomb (Yukawa) potentials on the bound ^1,3D states and the doubly excited ^1,3 D^e resonance states of helium atom using highly correlated exponential basis functions. The Density of resonance states are calculated using stabilization method. Highly correlated exponential basis functions are used to consider the correlation effect between the charged particles. A total of 18 resonances (nine each for ¹ D^e and ³ D^e states) below the n = 2 He ⁺ threshold has been calculated. For each spin states, this includes four members in the 2pnp series, three members in the 2snd series, and two members in 2pnf series. The resonance energies and widths for various screening parameters ranging from infinity to a small value for these ^1,3 D^e resonance states are reported along with the bound‐excited 1s3d ^1,3 D state energies. Overall behavior of the spectral profile of 1s3d ¹D state of helium atom due to electron‐electron and electron‐nucleus screening are also presented. Accurate resonance energies and widths are also reported for He in vacuum. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Atomistic simulation of site preference, Curie temperature, and lattice vibration of Nd2Co7 - xFex

The effects of Fe substitution for Co on the structural stability and the site preference of intermetallics Nd 2 Co 7-x Fe x with a hexagonal Ce 2 Ni 7-type structure are studied by using a series of interatomic pair potentials.In Nd 2 Co 7-x Fe x,Fe atoms are substituted for Co atoms with a strong preference for the 6h sites and the order of site preference is 6h,4e,4f,2a,and 12k.Calculated lattice parameters are found to be consistent with the reported results in the literature.The variation behaviour of the Curie temperature of Nd 2 Co 7-x Fe x is explained qualitatively by the exchange interaction model.The properties related to lattice vibration,such as phonon density of states and Debye temperature,are first evaluated for the Nd 2 Co 7-x Fe x compounds.