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The available experimental data for the elastic scattering of the isobar nuclei 6Li and 6He on 6 4 Zn have been reanalyzed in the available energy range using the optical model, double folding (DF) (Sao Paulo), and crystal model (CM). Double-folding (DF) and crystal model (CM) have been used to investigate the experimental data as a real part of the optical potential, while the imaginary part was taken in Woods–Saxon (WS) shape. One value of the real part of the optical potential has been applied to the two systems under consideration. The distance of the closest approach of the 6Li (6He) + 6 4 Zn systems has been extracted from the available experimental data using different methods. The extracted potential from the 6Li and 6He elastically scattered by 6 4 Zn data could be used as the basis for the creation of a simple global optical potential for 6Li and 6He. The extracted normalization factor ( N r ) was equal to the unity during the fitting process avoiding its unfortunate value (in the range 0.5–0.7) exists in the literature. It was observed that interaction distances vary slowly with the energy of the projectile and strongly depend on the projectile properties. The halo properties of 6He have a significant effect on the calculated reaction cross-sections. Different methods have been applied to 6He and 6Li elastically scattered by 6 4 Zn, where fair agreement between them has been observed. [ABSTRACT FROM AUTHOR]

The purposes of this study were: (1) to review the preparation and characterization of the intergrowth between goethite and hematite crystals; and (2) to propose a schematic diagram of the epitaxial relationships among three sets of (100) goethite twin crystals associated with the (001) orientation of the hexagonal prism of hematite. The Fe(ClO4)3 solution was prepared and aged at 70°C, which precipitated goethite initially and produced hematite later with prolonged aging. Goethite and hematite aged for 20 days were observed as star-shaped and hexagonal prisms, respectively. The results suggest that hematite could form later using goethite as a template surface. A selected area electron diffraction (SAED) pattern showed the epitaxial relationship among three sets of (100) goethite intergrowth crystals and hexagonal prisms with the (001) orientation of hematite. Goethite can be produced as lath-, X-, K-, or star-shaped crystals on the (100) orientation, depending on the Fe(ClO4)3 concentrations and the addition of HClO4 to Fe solution samples which were aged for a prolonged period at room temperature. The initial solubility products [(Fe3+)(OH–)3] of the sample solution, rather than the nature of the nuclei, are the key factors governing the formation of goethite or hematite. The addition of acids and high concentrations of iron solutions extend the secondary hydrolysis and induction period (IP) and favor the formation of hematite. The index of the SAED pattern of the star-shaped goethite intergrowth twin crystal has a (100) plane parallel to this basal plane and rotates at a 60° angle between two or three sets of lath-shaped goethite crystals, which share the (011) plane and form goethite twins with 'interpenetrated' crystal growth. Stereoscopic viewing using Oak Ridge Thermal Ellipsoid Plot (ORTEP) and CrystalMaker software was deployed to explore the relationship and configuration of oxygen atoms between pseudo-hexagonal (100) goethite associated with hexagonal (001) hematite lattice planes. A schematic diagram of the epitaxial relationship between star-shaped (100) goethite, which is acting as a template facilitating later precipitation of (001) hexagonal prisms of hematite on it, is presented. [ABSTRACT FROM AUTHOR]

Cellulose I crystals swell on exposure to ethylenediamine (EDA) molecules to form a cellulose I–EDA complex, and successive extraction of EDA molecules converts the complex crystalline phase to either original cellulose I or cellulose IIII, depending on the treatment procedure. The present study reports the extended ensemble molecular dynamics (MD) simulation of the cellulose I–EDA complex models. An accelerated MD simulation allows most of the EDA molecules to desorb from the crystal model through a hydrophilic channel between the piles of cellulose chains, one at a time. Migration of a single EDA molecule along the channel is simulated by the adopted steered MD method combined with the umbrella sampling method to evaluate the potential of mean force (PMF) or free energy change on its movement. The PMF continues to increase during the migration of an EDA molecule to give a final PMF value of more than 30 kcal/mol. The PMF profiles are largely lowered by the removal of EDA molecules in the neighboring channels and by the widening of the channel. The former suggests that the EDA desorption cooperates with that in the neighboring channels, and, in the latter case, an EDA migration is efficiently promoted by solvation with water molecules in the expanded channel. We conclude that the atomistic picture of the EDA desorption behaviors observed in the crystal models is applicable to the real crystalline phase. [ABSTRACT FROM AUTHOR]

The available experimental data for the elastic scattering of isobar nuclei 6Li and 6He on 1 2 C nuclei have been reanalyzed in a wide energy range of energy from 5.8 MeV to 600 MeV using the optical model with Distorted Wave Born Approximation (DWBA), and coupled reaction channel method (CRC) where inelastic scattering and transfer have been involved during calculations. A semi-microscopic potential, namely double-folding cluster model (DFC) has been used to investigate the cluster structure for both projectiles and target which was folded with Distorted Wave Born Approximation (DWBA) as a real part of potential where the imaginary part was taken in Woods–Saxon (WS) shape. The crystal model method has been applied to 6Li, 6He elastically scattered by 1 2 C, and reliable analysis of the considered experimental data has been obtained. [ABSTRACT FROM AUTHOR]

Abstract: The various crystal models of cellulose Iβ, each differing in crystal size, have been studied by computer simulation using the amber molecular-dynamics package and the GLYCAM parameters. The four types of crystal model were constructed by a combination of two base-plane sizes, consisting of either 24 or 48 chains and two chain lengths having either 10 or 20 residues. The base planes of the crystal models were composed by the edges of the [1,1,0], [1,−1,0], and [1,0,0] crystal planes, where the [1,1,0] plane was assigned to the longest edge. The crystal models were soaked in water boxes to investigate their swelling behavior. Unexpectedly, the crystal models twisted quickly to form a slightly right-handed shape during the initial ∼50ps and that, in a steady, swollen state, the twisted forms remained for the rest of the simulation time. In spite of such overall deformation, the inner part of the swollen model fairly reproduced the important structural features of the original crystal structure, such as the rotational positions of the substituent groups and the hydrogen-bonding scheme. On heating the crystal model up to 550K, the twisted shape was conserved in most of the temperature range, while the initial conformations of the substituent groups deviated above ∼430K, followed by appreciable disordering in chain sheets at higher temperatures. It is suggested that some internal tensions are involved within a chain sheet of the initial structure. In the course of swelling, some of these tensions were released to introduce a twisted shape in the crystal models. [Copyright &y& Elsevier]