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Studies on high pressure-high temperature synthesis of carbon clathrates

Leszczyński J., Wojciechowski K., Koleżyński A., Klimczyk P.

Mechanik

2016

R. 89, nr 5-6

512--513

Ab initio DFT calculations were used for theoretical analysis of crystal and electronic structure of C46, Li8C46 and Li8B6C40 carbon clathrates. Simultaneously experimental attempts of carbon clathrates synthesis from fullerene C60 at pressure 8 GPa were made. For a specific conditions polymerized form of fullerene – fullerite was obtained.

Przeprowadzono obliczenia ab initio metodą DFT w celu analizy struktury krystalicznej i elektronowej hipotetycznych klatratów węglowych C46, Li8C46 i Li8B6C40. Jednocześnie podjęto próby syntezy klatratów węglowych z fullerenu C60 pod ciśnieniem 8 GPa. W pewnych warunkach otrzymano spolimeryzowaną formę fullerenu – fulleryt.

Preparation, Magnetic Studies and Band Structure Calculation of NiFe2O4 Nanoparticles

Nabiyouni G., Fesharaki M., Zolotovsky A.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

2011

Vol. 15, No 1

107-119

We have undertaken a comprehensive theoretical study of the band structure, density of states, dependence of the Curie point and saturation magnetization on the size of NiFe2O4 nanoparticles prepared by the conventional ceramic method. Commercially available NiFe2O4 powder was first annealed in an oxygen environment in a furnace at 1100oC for 3h. The X-ray diffraction pattern indicated that the sample was single-phase at this stage. The average grain size estimated by scanning electron microscopy (SEM) was in the range of 300 to 350nm. The magnetic behavior of the sample at room temperature was studied by means of a superconducting quantum interference device (SQUID). The Curie temperature of the nickel ferrite powder was measured using an LCR meter. The measurement of the Curie temperature and saturation magnetization indicated that a decrease in the grain size leads to a decrease in the Curie temperature and in the saturation magnetization. The small value of saturation magnetization was attributed to a spin-glass-like surface layer on the nanocrystalline nickel ferrite with a ferrimagnetically aligned core (H.Nathani and S.Gubbala 2004 J.Mater. Sci. and Engin. B 111 95). Good agreement was obtained between theory and experimental results.