Univerzita PardubiceFakulta chemicko- technologická

Univerzita Pardubice

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Publikace detail

Amorphous TeGeI: Structure and Comparison with Similar Systems

Autoři: Voleská Iva | Akola Jaakko | Wágner Tomáš

Rok: 2011

Druh publikace: ostatní do riv

Strana od-do: nestránkováno

Tituly:

Jazyk	Název	Abstrakt	Klíčová slova
cze	Amorphous TeGeI: Structure and Comparison with Similar Systems	The amorphous TeGeI and TeGeGa or TeGeSe systems are derived from GeTe and Ge2Sb2Te5 materials. [1, 2] The materials are known as the chalcogenide covalently bonded glasses. The Te-based materials have properties as semiconductivity, reversible amorphous-crystal phase changes, and transparent in IR region. The calculations were performed within the periodic DFT model, using the CPMD code. [3] The periodic model of the simple cubic unit cell of TeGeI (Te78Ge11I11) system contained 216 atoms. The equilibrium volume of unit cell was fitted from experimental density at temperature 300 K. [4] The structure of samples was based on the GST geometry. The PBEsol [5] as exchange-correlation functional with Troullier-Martins pseudopotential [6] and plane-wave basis set with a kinetic energy cut-off 20 Ry were used. The Brillouin zone sampling was restricted to the single point (k = 0). The Nosé-Hoover thermostat with frequency 800 cm-1, NVT ensemble and times step 0.1694 fs as parameters for BOMD was used. The sample was heated to temperature 600 K (T > Tg) and later cooled to temperature 300 K in 50 K steps. The final geometry and two snapshots of TeGeI were studied. The bond order distributions and the bond strenght maps for atom pairs were analyzed. The partial distribution functions were plotted: the model is containing more GeI than ITe bonds. The total coordination numbers with radial cutoff of 3.2 Å and average effective charges of elements (Bader, Voronoi, Mulliken) [7] were calculated. The same properties and parameters are analyzed for TeGeGa and TeGeSe. The results can be compared with experimental data (EXAFS, X-ray and neutron diffraction).	chalkogenidové sklo; molekulární modelování; struktura; DFT; telur
eng	Amorphous TeGeI: Structure and Comparison with Similar Systems	The amorphous TeGeI and TeGeGa or TeGeSe systems are derived from GeTe and Ge2Sb2Te5 materials. [1, 2] The materials are known as the chalcogenide covalently bonded glasses. The Te-based materials have properties as semiconductivity, reversible amorphous-crystal phase changes, and transparent in IR region. The calculations were performed within the periodic DFT model, using the CPMD code. [3] The periodic model of the simple cubic unit cell of TeGeI (Te78Ge11I11) system contained 216 atoms. The equilibrium volume of unit cell was fitted from experimental density at temperature 300 K. [4] The structure of samples was based on the GST geometry. The PBEsol [5] as exchange-correlation functional with Troullier-Martins pseudopotential [6] and plane-wave basis set with a kinetic energy cut-off 20 Ry were used. The Brillouin zone sampling was restricted to the single point (k = 0). The Nosé-Hoover thermostat with frequency 800 cm-1, NVT ensemble and times step 0.1694 fs as parameters for BOMD was used. The sample was heated to temperature 600 K (T > Tg) and later cooled to temperature 300 K in 50 K steps. The final geometry and two snapshots of TeGeI were studied. The bond order distributions and the bond strenght maps for atom pairs were analyzed. The partial distribution functions were plotted: the model is containing more GeI than ITe bonds. The total coordination numbers with radial cutoff of 3.2 Å and average effective charges of elements (Bader, Voronoi, Mulliken) [7] were calculated. The same properties and parameters are analyzed for TeGeGa and TeGeSe. The results can be compared with experimental data (EXAFS, X-ray and neutron diffraction).	chalcogenide glass; molecular modeling; periodic DFT; Tellurium; structure