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Title:Characterization of Mg low-index surfaces by first-principles
Authors:Gunde, Miha (Author)
Martin Samos Colomer, Layla (Mentor) More about this mentor... New window
Files:.pdf Miha_Gunde.pdf (1,77 MB)
Work type:Master's thesis/paper (mb22)
Tipology:2.09 - Master's Thesis
Organization:FN - School of Science
Abstract:In this work, three surfaces, namely, Mg(0001), Mg(10 ̄1 0) and Mg(11 ̄2 0) are investigated by means of Density Functional Theory and Generalized Gradient Approximation first-principle calculations. The surfaces have been characterized in terms of their interlayer distances, surface energies, Projected Density of States and Surface Core Level Shifts. Contrary to what was found in previous studies based on Density Functional Theory-Local Density Approximation, the use of Generalized Gradient Approximation exchange correlation functional unravels the oscillatory behavior of both interlayer distances and Surface Core Level Shifts of Mg(10 ̄1 0). Moreover, the Projected Density Of States of un-reconstructed Mg(11 ̄2 0) exhibit the typical quantisation of electronic levels associated to a 2D-confinement of a 3D nearly-free electron gas, as observed in nano-wires, and a Peierls instability along the unconfined direction. Different possible reconstructions on Mg(11 ̄2 0) have then been investigated. In particular, it is found that the surface energy of (2X1) and (3X1) reconstructions is almost degenerate and lower than the surface energy of the unreconstructed Mg(11 ̄2 0) surface. Because of the quasi-degeneracy of surface energies, Mg(11 ̄2 0) surface should be composed by a combination of all the quasi degenerate phases.
Keywords:Density Functional Theory, first-principle calculations, Mg surface, Surface Core-Level Shift, surface relaxation, surface reconstruction
Year of publishing:2017
Source:Nova Gorica
COBISS_ID:4836859 Link is opened in a new window
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Secondary language

Title:Karakterizacija Mg površin nizkih indeksov iz osnovnih principov
Abstract:Delo obravnava tri kristalografske ravnine, Mg(0001), Mg(10 ̄1 0) in Mg(11 ̄2 0), iz osnovnih principov s teorijo gostotnega funkcionala (Density Functional Theory) v približku posplošenega gradienta (Generalized Gradient Approximation). Obravnavane površine so določene z medravninskimi razdaljami, površinskimi energijami, projecirano gostoto stanj (Projected Density of States) in premiki nivojev notranjih lupin. V nasprotju z rezultati raziskav, narejenih z uporabo teorijo gostotnega funkcionala v približku lokalne gostote, pa uporaba približka posplošenega gradienta izmenjalnega korelacijskega funkcionala pokaže oscilacije medravninskih razdalj in oscilacije premikov nivojev notranjih lupin površine Mg(10 ̄1 0). Projecirana gostota stanj nerekonstruirane površine Mg(11 ̄2 0) kaže tipično kvantizacijo elektronskih nivojev, ki je značilna za 2D-omejen skoraj prosti 3D plin elektronov, kot je opaženo v nanožičkah. Vzdolž smeri brez prostorske omejenosti se pojavi tudi Peierlsova nestabilnost. Raziskane so bile različne možne rekonstrukcije površine Mg(11 ̄2 0). Ugotovljeno je bilo, da površin- ski energiji rekonstrukcij (2X1) in (3X1) skoraj degenerirata in sta manjši od površinske energije nerekonstruirane površine Mg(11 ̄2 0). Zaradi kvazi-degeneracije površinskih energij je površina Mg(11 ̄2 0) najverjetneje sestavljena kot kombinacija vseh kvazi-degeneriranih stanj.
Keywords:Teorija gostotnega funkcionala, osnovni principi, površina Mg, premiki nivojev notranjih lupin površine, relaksacija površine, rekonstrukcija površine