Typeset Using Revt E X 2
نویسنده
چکیده
The structure and the electronic properties of a sodium tetrasilicate (Na2Si4O9) glass were studied by combined Car-Parrinello and classical molecular-dynamics simulations. The glass sample was prepared using a method employed recently in a study of a silica glass [M. Benoit et al, Euro. Phys. J. B 13, 631 (2000)]. First we generated a NS4 glass by classical molecular-dynamics and then we took it as the initial configuration of a first-principles molecular-dynamics simulation. In the ab initio moleculardynamics simulations, the electronic structure was computed in the framework of the Kohn-Sham density functional theory within the generalized gradient approximation using a B-LYP functional. The Car-Parrinello dynamics is remarkably stable during the considered trajectory and, as soon as it is switched on, some significant structural changes occur. The ab initio description improves the comparison of the structural characteristics with experimental data, in particular concerning the Si-O and Na-O bond lengths. From an electronic point of view, we find that the introduction of the sodium oxide in the silica network lowers the band gap and leads to a highly non-localized ∗Author to whom correspondence should be addressed: [email protected]
منابع مشابه
Adjoint \quark" Color Elds in Four-dimensional Lattice Gauge Theory: Vacuum Screening and Penetration Typeset Using Revt E X
The elds generated by \quarks" in the adjoint representation of SU(2) color are analyzed in the scaling region of the four-dimensional lattice theory. Evidence of vacuum screening of adjoint quarks is obtained from a comparison of quark-antiquark (QQ) ux-tubes for quarks in the adjoint (\isospin" j = 1) and fundamental (j = 1=2) representations. The component E j of the colorelectric eld streng...
متن کاملTypeset Using Revt E X 1
The HQET/NRQCD Lagrangian is computed to order α/m3. The computation is performed using dimensional regularization to regulate the ultraviolet and infrared divergences. The results are consistent with reparametrization invariance to order 1/m3. Some subtleties in the matching conditions for NRQCD are discussed. Typeset using REVTEX 1
متن کاملX-ray Photoemission Study of Nis 2−x Se X (x = 0.0 -1.2) Typeset Using Revt E X 1
Electronic structure of NiS2−xSex system has been investigated for various compositions (x) using x-ray photoemission spectroscopy. An analysis of the core level as well as the valence band spectra of NiS2 in conjunction with many-body cluster calculations provides a quantitative description of the electronic structure of this compound. With increasing Se content, the on-site Coulomb correlatio...
متن کاملInfrared and Raman Studies of the Verwey Transition in Magnetite. Typeset Using Revt E X 2
We present infrared and Raman measurements of magnetite (Fe3O4). This material is known to undergo a metal-insulator and a structural transition (Verwey transition) at TV = 120 K. At temperatures below TV, we observe a
متن کاملInteresting Magnetic Properties of Fe 1−x Co X Si Alloys Typeset Using Revt E X
Solid solution between nonmagnetic narrow gap semiconductor FeSi and diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with longrange helical magnetic ordering, for a wide range of intermediate concentration. We report various interesting magnetic properties of these alloys, including low temperature re-entrant spin-glass like behaviour and a novel inverted magnetic hysteres...
متن کامل