Calculation Of Different Properties Research Articles

First-Principle Study on Correlate Structural, Electronic and Optical Properties of Ce-Doped BaTiO3

The structural, electronic, and optical properties of pure and Ce-doped BaTiO3 were investigated based on first-principle calculation. Here, we concentrate on understanding the effect of the substitution of Ce for Ba and Ti sites in the equilibrium lattice parameters, DOS, electronic band structure, and optical performance of the materials. The crystal structures with a 12.5% doping ratio at different sites were constructed by superseding an atom of Ba (or Ti) site with a Ce atom and investigating the optimized crystal structure parameters. The substitution of Ce leads to a reduction in the band gap by inducing the movement of the conduction band minimum (CBM) and valence band maximum (VBM). The reduction in the band gap has been shown to be beneficial in increasing electrical conductivity. The density of states of the materials was calculated to gain insight into the valence band, conduction band, and contribution of each orbital to the total density of states in the electronic structure. The charge density, Mulliken charges, and bond overlap populations of pristine and Ce-doped BaTiO3 were calculated to understand the nature of chemical bonds before and after doping. In addition, the optical properties of the materials were calculated, and the substitution of Ce for Ba site increased the static dielectric constant. In contrast, it decreased when Ce was doped into the Ti site. The substitution of Ce for different sites reduced the reflectivity of the material, while the transparency of the materials before and after doping was almost the same. The materials were transparent to incident light when the photon energy was below 10 eV, whereas opacity was in the ultraviolet range of 10–13 eV and beyond 20 eV. The theoretical calculation of different properties provides a new idea for the theoretical study of the BaTiO3-based system.

Different Properties of the $$\varvec{\bar{K}NN}$$ K ¯ N N and $$\varvec{\bar{K}\bar{K}N}$$ K ¯ K ¯ N Systems

A series of exact or accurate three-body calculations of different properties of the \(\bar{K}NN\) and \(\bar{K}\bar{K}N\) systems is described. In particular, binding energies and widths of the quasi-bound states in the systems were calculated. Near-threshold elastic \(K^- d\) amplitudes were also found together with the 1s level shift and width of kaonic deuterium. Different dependences of the three-body results on two-body inputs are discussed.

Development of the configuration-interaction + all-order method and application to the parity-nonconserving amplitude and other properties of Pb

We have further developed and extended a method for calculation of atomic properties based on a combination of the configuration interaction and coupled-cluster approach. We have applied this approach to the calculation of different properties of atomic lead, including the energy levels, hyperfine structure constants, electric-dipole transition amplitudes, and E1 parity nonconserving (PNC) amplitude for the (6p^2) ^3P_0 - (6p^2) ^3P_1 transition. The uncertainty of the E1 PNC amplitude was reduced by a factor of two in comparison with the previous most accurate calculation [V.~A.~Dzuba et.al., Europhys. Lett. 7, 413 (1988)]. Our value for the weak charge Q_W=-117(5) is in agreement with the standard model prediction.

Multiscale simulations of protein landscapes: Using coarse‐grained models as reference potentials to full explicit models

Evaluating the free-energy landscape of proteins and the corresponding functional aspects presents a major challenge for computer simulation approaches. This challenge is due to the complexity of the landscape and the enormous computer time needed for converging simulations. The use of simplified coarse-grained (CG) folding models offers an effective way of sampling the landscape but such a treatment, however, may not give the correct description of the effect of the actual protein residues. A general way around this problem that has been put forward in our early work (Fan et al., Theor Chem Acc 1999;103:77-80) uses the CG model as a reference potential for free-energy calculations of different properties of the explicit model. This method is refined and extended here, focusing on improving the electrostatic treatment and on demonstrating key applications. These applications include: evaluation of changes of folding energy upon mutations, calculations of transition-states binding free energies (which are crucial for rational enzyme design), evaluations of catalytic landscape, and evaluations of the time-dependent responses to pH changes. Furthermore, the general potential of our approach in overcoming major challenges in studies of structure function correlation in proteins is discussed.

Slater's Exchange Parameters α for Analytic and Variational Xα Calculations.

Recently, we formulated a fully analytical and variational implementation of a subset of density functional theory using Gaussian basis sets to express orbital and the one-body effective potential. The implementation, called the Slater-Roothaan (SR) method, is an extension of Slater's Xα method, which allows arbitrary scaling of the exchange potential around each type of atom in a heteroatomic system. The scaling parameter is Slater's exchange parameter, α, which can be determined for each type of atom by choosing various criteria depending on the nature of problem undertaken. Here, we determine these scaling parameters for atoms H through Cl by constraining some physical quantity obtained from the self-consistent solution of the SR method to be equal to its exact value. Thus, the sets of α values that reproduce the exact atomic energies have been determined for four different combinations of basis sets. A similar set of α values that is independent of a basis set is obtained from numerical calculations. These sets of α parameters are subsequently used in the SR method to compute atomization energies of the G2 set of molecules. The mean absolute error in atomization energies is about 17 kcal/mol and is smaller than that of the Hartree-Fock theory (78 kcal/mol) and the local density approximation (40 kcal/mol) but larger than that of a typical generalized gradient approximation (∼8 kcal/mol). A second set of α values is determined by matching the highest occupied eigenvalue of the SR method to the negative of the first ionization potential. Finally, the possibility of obtaining α values from the exact atomization energy of homonuclear diatomic molecules is explored. We find that the molecular α values show much larger deviation than what is observed for the atomic α values. The α values obtained for atoms in combination with an analytic SR method allow elemental properties to be extrapolated to heterogeneous molecules. In general, the sets of different α values might be useful for calculations of different properties using the analytic and variational SR method.

Multiskyrmions and baryonic bags

Analytical treatment of skyrmions given by rational map (RM) ansatz proposed recently for the Skyrme model is extended for the model including the sixth-order term in chiral field derivatives in the Lagrangian and used for calculations of different properties of multiskyrmions. At large baryon numbers the approximate solutions obtained are similar to the domain wall, or spherical bubbles with energy and baryon number density concentrated at their boundary. A rigorous upper bound is obtained for the masses of RM multiskyrmions which are close to known masses, especially at large B. For the sixth-order variant the lower bound for the masses of RM skyrmions is obtained as well. The main properties of the bubbles of matter are obtained for an arbitrary number of flavours. They are qualitatively the same for the fourth- and sixth-order terms present in the Lagrangian, although differ in some details.

Lagrange-mesh calculations of halo nuclei

In the Lagrange-mesh technique, a variational calculation takes the form of a mesh calculation with the help of the Gauss-Laguerre quadrature, without losing its accuracy. A simplified and improved version of the method is applied to calculations of different properties of three-body systems involving a point cluster and two neutrons, with effective cluster-neutron and neutron-neutron forces. The technique leads to a standard diagonalization of large but sparse matrices. Wave functions are available in analytical form. The 6He, 11Li and 14Be halo nuclei are studied and discussed. Matter radii agree with experiment when the binding energies are correctly reproduced with a renormalization of the core-neutron interactions. For 11Li, the need for a low-lying virtual state in this interaction is confirmed. The origin of the binding is analyzed by looking at the different contributions to the energy and at components of the wave function. Asymptotic normalizations, form factors and densities are also determined.

Comparative Molecular Field Analysis (CoMFA) of MX Compounds using different Semi‐empirical Methods: LUMO Field and its Correlation with Mutagenic Activity

AbstractIn the present paper we make a comparison among three different semi‐empirical methods (AMI, MNDO and PM3) for the optimization of the geometries and calculation of different properties of MX compounds. The results were used to develop a CoMFA model to correlate the TA100 mutagenicity of these compounds with the LUMO field. The correlations between the LUMO field and steric, electrostatic and CoMFA fields generated automatically by the SYBYL CoMFA program, were explored. A comparison among different values of grid spacing for the lattice and standard deviation thresholds for column filtering was carried out to select the best values for this and future work.The results indicate that AM1 and PM3 methods represent a real improvement over MNDO in respect to QSAR studies relating electronic properties and mutagenicity for these compounds.