Structural and magnetic properties of Iron clusters

Electronic, magnetic, and chemical properties of Fe nanoparticles are of particular interest for materials science, engineering, and metallurgical applications, including biomedical applications (e.g., medical imaging, cancer treatment, etc.). In this study, we search for the most stable geometries of the Fe clusters, Fen, up to n=8. Binding energies, magnetic moments, bond lengths, bond angles, and charge densities of clusters are computed and compared to the available experimental data. The various cluster isomers were examined energetically. We found that, in general, higher dimensional geometries are more stable than lower dimensions (i.e., 1-dimension or 2-dimension). Calculations for the Fe dimer yield a bond length of 1.98 angstroms, which appears to agree with experimental values (1.87 angstroms [1]). The most stable Fe trimer is an isosceles triangle. The stable geometry for n=4 is a tetrahedron. For Fe5 and Fe6, the stable geometries are trigonal bipyramidal and octahedral, respectively. The average magnetic moment per atom is 2.5-3.0 Bohr magnetons; this result is in agreement with previous theoretical results. Potential future work includes studies of Fe clusters with n\u3e8, IR vibrational spectra calculations, and studies of Fe clusters encapsulated by C60 fullerene nanocontainers

Fluorine Chemistry at Extreme Conditions: Possible Synthesis of Hgf4

By irradiating a pressurized mixture of a fluorine-bearing compound (XeF2XeF2) and HgF2HgF2 with synchrotron hard x-rays ... (See full text for complete abstract

Leisure Activity, Ethnic Preservation, and Cultural Integration of Older Korean Americans

For immigrant groups, leisure activity has the potential both to increase familiarity with a new culture and to preserve cultural history and identity. Using a qualitative case study design, this research analyzed leisure activities of six older Korean Americans to determine both personal and cultural meanings of leisure. From a personal perspective, leisure was used to create two effects for the older adults: Ki-Bun-Chun-Whan, which is the experience of a shift in emotional atmosphere as a result of engaging in activities; and self-development activities, which provide the older adults with opportunities for learning or growth. Cultural meanings of leisure activities included the re-creation of Koreanness and the reliance on familiar patterns to create a sense of security in a still-strange land. Thus, with the individuals studied in this investigation, leisure activities were used more often for continuity and ethnic preservation than for cultural integration. Social workers can use leisure activities as avenues to increase knowledge and social participation, but they should also take into account the need to preserve cultural and collective identity in older immigrants

Universal Expression for the Lowest Excitation Energy of Natural Parity Even Multipole States

We present a new expression for the energy of the lowest collective states in even-even nuclei throughout the entire periodic table. Our empirical formula is extremely valid and holds universally for all of the natural parity even multipole states. This formula depends only on the mass number and the valence nucleon numbers with six parameters. These parameters are determined easily and unambiguously from the data for each multipole state. We discuss the validity of our empirical formula by comparing our results with those of other studies and also by estimating the average and the dispersion of the logarithmic errors of the calculated excitation energies with respect to the measured ones.Comment: 10 pages, 5 figure

First-Principles Structural, Mechanical, and Thermodynamic Calculations of the Negative Thermal Expansion Compound Zr2(WO4)(PO4)2

The negative thermal expansion (NTE) material Zr2(WO4)(PO4)2 has been investigated for the first time within the framework of the density functional perturbation theory (DFPT). The structural, mechanical, and thermodynamic properties of this material have been predicted using the Perdew, Burke and Ernzerhof for solid (PBEsol) exchange–correlation functional, which showed superior accuracy over standard functionals in previous computational studies of the NTE material α-ZrW2O8. The bulk modulus calculated for Zr2(WO4)(PO4)2 using the Vinet equation of state at room temperature is K0 = 63.6 GPa, which is in close agreement with the experimental estimate of 61.3(8) at T = 296 K. The computed mean linear coefficient of thermal expansion is −3.1 × 10–6 K−1 in the temperature range ∼0–70 K, in line with the X-ray diffraction measurements. The mean Grüneisen parameter controlling the thermal expansion of Zr2(WO4)(PO4)2 is negative below 205 K, with a minimum of −2.1 at 10 K. The calculated standard molar heat capacity and entropy are CP0 = 287.6 and S0 = 321.9 J·mol–1·K–1, respectively. The results reported in this study demonstrate the accuracy of DFPT/PBEsol for assessing or predicting the relationship between structural and thermomechanical properties of NTE materials

Investigation of structural and magnetic properties of iron clusters encapsulated in carbon

Our goal is to investigate and predict the properties of iron-carbon nanostructures by performing numerical calculations using the density-functional theory. We are interested in which nanostructures are most stable, and in how they are likely to form. We have a particular interest in the magnetic properties of carbon buckyballs containing iron particles. These structures have potential for biomedical application, including use in anti-cancer treatment. Lone iron clusters have potential for use as a catalyst designed to reduce vehicle emissions

The Effects of pressure on wide bandgap GaN semiconductors

Gallium nitride (GaN) is a group-III nitride semiconductor; which may prove useful in developing optical instruments that operate under high ambient pressures. The purpose of this project is to examine the properties of GaN under varying conditions. The methods used in this experiment consist of modeling free energy as a function of lattice constants; calculating bond lengths, bond strengths, and bulk moduli; and comparing the resultant data with values in published literature. We will also compare these results with experimental data drawn from x-ray diffraction scans. By doing so, we hope to determine whether gallium nitride is suitable for use as a semiconductor at high pressures