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success in calculating these quantities of synthesized SMMs,however, discussion about magneto-structural correlationsof SMMs as well as suggestion for designing new SMMs arestill missing. In this study, we focus on exploring magnetostructuralcorrelations of a fascinating SMM system, i.e.distorted cubane Mn 4+ Mn 3+ 3 SMMs based on Densityfunctionaltheory (DFT), to support for tailoring J ij of SMMs,as well as for designing high T B SMMs.Firstly, our calculated results demonstrate that intramolecularexchange coupling of known Mn 4+ Mn 3+ 3 SMMs is dominatedby antiferromagnetic (AFM) couplings between the Mn 4+ ionsand the three Mn 3+ ions resulting in a ferrimagnetic structureand S T = 9/2 consistent with the experimental observation. Themechanism of AFM Mn 4+ -Mn 3+ coupling (J AB ) is determinedby delocalization of 3d electrons from the d z 2 orbitals at theMn 3+ sites to the t 2g orbitals at the Mn 4+ site through ligandorbitals which results in the π-like hybridization states amongthese orbitals just below the Fermi level. These results allowsus to predict that J AB will be strongest when the Mn 3+ -L-Mn 4+exchange coupling angle α ≈ 90 o , while synthesized Mn 4SMMs have α ≈ 95 o .Secondly, by rational variations in ligands, novel Mn 4+ Mn 3+ 3SMMs, having S T of 9/2, α in a range of 88.5 o −95.5 o , andJ AB /k B in a range of −36.77 K to −214.79 K, have beendesigned. The results confirm the correlation between J ABand α. Moreover, this work reveals first possibilities ofadopting N based ligands, NR’ (R’ = a radical), to formexcellent exchange pathways between Mn ions in Mn 4 SMMs.Adopting N based ligands to form exchange pathwaysbetween Mn ions can enhance three times of J AB incomparison to using O. Variation in the R’ radical isdemonstrated as an effective way to tailor and optimize theexchange pathways between Mn ions.In conclusion, we have succeeded in exploring magnetostructuralcorrelation in Mn 4 SMMs based on DFT. Theresults strongly support for synthesizing new superior Mn 4SMMs with strong intramolecular exchange coupling.Người trình bày: Nguyễn Anh Tuấn90. First Principle Study on AlN Nano WireVũ Ngọc Tước, Nguyễn Viêt MinhWe present a first-principle study on the atomic andelectronic structure of AlN Nanowire and examine thedepedence of surface stress on Nanowire lateral size andshape. The hexagonal wire size ranging as 10-16-22and triangular wire ranging from 10-13-16-20. Weinvestigate the unsaturated dangling bond state in theregion of bandgap with varying the wire’s diameter. Wealso calculated the surface formation energy and findthat it decrease with increasing the wire diameter and agreater stability (lower surface formation energy) comeswith hexagonal wires. We also study the dependence oftheoretical prediction on various DFT functionaltreatment using Dmol3 local orbital density functionalmethod with an effective core potential.Người trình bày: Vũ Ngọc Tước91. Computer Simulation of Microstructure inDisordered SystemsLê Thế Vinh, Nguyễn Minh Quân, Dương CôngHiệp, Nguyễn Thành Tín, Nguyễn Tất Đạt, ĐổngQuốc ViệtComputer simulation will be done to determine the localstructure of disordered system. Twenty-four systems ofSiO2, (Al2O3)x(SiO2)1-x, Co-B and Co-P at differentdensities is prepared by compressing the low-density.The microstructure will be analyzed through the pairradial distribution function, bond-angle distributionThành phố Đồng Hới (03- 06/8/2009) Trang 79/ 102 Thành phố Đồng Hới (03- 06/8/2009) Trang 80/ 102
and the characteristics of voids and void aggregations.We focused on two kinds of void aggregations: voidclusters and void tubes.Người trình bày: Lê Thế Vinh92. Investigation of Thermodynamic Properties ofLiquid Transition MetalsLê Hoàng Anh, Đỗ Phương LiênWe present a study of thermodynamic properties ofliquid transition metals. The cohesive energies and theheats of fusion have been calculated in the bond-orderapproach coupled with the cluster Bethe lattice methodfor 3d, 4d and 5d liquid transition metals, taking inaccount s-d hybridization which is treated selfconsistently.The results obtained are in good agreementwith experimental data. An analyze of the contributionsrelated to the s- and d-electrons to the cohesive energiesare realized and showed that s-electrons play animportant part in the cohesion of liquid transitionmetals. The tendencies of thermodynamic properties forthree series have been also discussed. So far, our work isthe first systematic study of properties of cohesion of allthe transition metals in their liquid phases.Người trình bày: Lê Hoàng Anh93. Investigation of Structural and ElectronicPropertiesof Liquid Transition Metals and TheirAlloysLê Hoàng Anh, Đỗ Phương LiênThành phố Đồng Hới (03- 06/8/2009) Trang 81/ 102We present a study of structural and electronicproperties of 3d, 4d and 5d liquid transition metals andtheir alloys by calculating the interatomic potentials inthe tight-binding bond-order approach coupled with thecluster Bethe lattice method and realizing dynamicmolecular simulations The results method are in goodagreement with accurate diffraction data. Thetendencies of properties for three series have been alsodiscussed. So far, our work is the first systematic studyof structural and electronic properties of all thetransition metals in their liquid phases.Người trình bày: Lê Hoàng Anh94. The Operator Method for non-PerturbationCalculations of Hydrogen Spectra in aMagnetic Field of Arbitrary StrengthNguyễn Phương Duy Anh, Nguyễn Văn Hòa, LêVăn HoàngBy using the Laplace transformation we apply theoperator method (OM) directly to the problem of ahydrogen atom in a magnetic field of arbitrary strength.The high-order corrections are calculated by both theperturbation theory and the iterative procedure andthen compare each to other. The correction series arerapidly convergent that allow us to obtain exactnumerical solutions for the considered problem.Người trình bày: Nguyễn Phương Duy Anh95. Density-Functional Study of Jahn-Teller Effectin BaTiO3Thành phố Đồng Hới (03- 06/8/2009) Trang 82/ 102
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Page 5 and 6: [P - 27] Vũ Ngọc Sáu, B. Brzost
Page 7 and 8: Hoàng Đình Tiến, Ngô Văn Tha
Page 9 and 10: [P - 64] Lê Hoàng Anh, Đỗ Phư
Page 11 and 12: HỘI NGHỊ VẬT LÝ LÝ THUYẾT
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Page 25 and 26: Nguyễn Quang Báu, Nguyễn Văn
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