Ab-initio Calculations of the Electronic Structure and Cohesive Properties of the Orthorhombic Oxynitrides X2N2O (X = C, Si, Ge)

Ivanovskiĭ, A. L.; Medvedeva, N. I.; Kontsevoi, Oleg Y.; Швейкин, Г. П.

doi:10.1002/1521-3951(200010)221:2<647::aid-pssb647>3.0.co;2-b

Cited by 9 publications

(6 citation statements)

References 33 publications

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“…Its crystal structure is shown in Figure a. The structure of this crystal is analogous to a known crystal structure of Si 2 N 2 O and has also been investigated theoretically at ambient conditions by following this analogy and replacing Si with C. , Our calculations show that it is thermodynamically stable from 10 to 100 GPa and does not have imaginary bands in the phonon dispersion curves at 0 GPa . The phonon dispersion curves rely on the harmonic expansion of the energy, however at higher temperatures anharmonic terms in the expansion may become relevant.…”

Section: Resultsmentioning

confidence: 99%

Ternary Inorganic Compounds Containing Carbon, Nitrogen, and Oxygen at High Pressures

Steele

Oleynik

2017

Inorg. Chem.

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Ternary CNO compounds are actively researched as novel high energy density and ultrahard materials. Although some synthesis work has been performed at ambient conditions, very little is known about the high pressure chemistry of of CNO compounds. In this work, first-principles variable-composition evolutionary structure prediction calculations are performed with the goal of discovering novel mixed CNO materials at ambient and high pressure conditions. By systematically searching ternary variable composition crystalline materials, the full ternary phase diagram is constructed in the range of pressures from 0 to 100 GPa. The search finds the CNO crystal containing an extended covalent network of C, N, and O atoms, having space group symmetry Cmc2, and stable above just 10 GPa. Several other novel metastable (CO)-(N) crystalline compounds discovered during the search, including two polymorphs of CNO and two polymorphs of CNO crystals, are found to be energetically favorable compared to polymeric carbon monoxide (CO) and nitrogen. Predicted new compounds are characterized by their Raman spectra and equations of state.

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Section: Resultsmentioning

confidence: 99%

Ternary Inorganic Compounds Containing Carbon, Nitrogen, and Oxygen at High Pressures

Steele

Oleynik

2017

Inorg. Chem.

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“…Our calculated structural data is also quite consistent with values obtained in earlier theoretical studies. 22,25,27 The structural parameters of the hypothetical R-SiGeN 2 O and β-SiGeN 2 O polytypes are predicted to be virtually identical. We note that the molar volume of the β-polymorph is found to be slightly lower than that of its R-counterpart, which may be associated with the slightly different packing obtained upon layering the SiN 3 O and GeN 2 O polyhedral units.…”

Section: Molecular Properties Of Gasmentioning

confidence: 99%

“…The band structure of the prototypical Si 2 N 2 O system has been previously ,, studied using DFT-LDA methods using a variety of methodologies including full potential linearized muffin-tin (FLMTO) and the orthogonalized linear combination of atomic orbitals (OLCAO), resulting in some ambiguity in the quantatitve outcome at the same level of theory. The most striking discrepancies involve the band widths and band gaps ( E g ).…”

Section: Properties Of Solid State Si2n2o Ge2n2o and Sigen2omentioning

confidence: 99%

“…Although a considerable theoretical and experimental knowledge-base exists for the reactants (SiH 3 ) 2 O − and (GeH 3 ) 2 O − and products Si 2 N 2 O ,− and Ge 2 N 2 O − in eq and , the corresponding properties of the SiH 3 OGeH 3 species and solid SiGeN 2 O phases in reaction eq are completely unknown. Accordingly the relationship between the properties of the asymmetrical analogues and the average behavior of the corresponding Si- and Ge- based molecules and solids is of considerable interest.…”

Section: Introductionmentioning

confidence: 99%

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Si−Ge-based Oxynitrides: From Molecules to Solids

2010

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Density functional theory simulations are used to predict ground state crystal structures, electronic properties, and thermodynamic stability of a new class of Si 1-x Ge x N 2 O oxynitride materials with potential applications as tunable dielectrics. Thermochemical simulations are also used to explore their possible synthetic routes via reactions of ammonia with (a) mixtures of (SiH 3 ) 2 O and (GeH 3 ) 2 O, and (b) a singlesource heteronuclear analogue SiH 3 OGeH 3 . To obtain quantitative values for the above reaction energies we implement a consistent computational methodology to simulate the structural and thermochemical properties of both molecular and solid state reactants and products at finite-temperature. In the case of the wellknown (SiH 3 ) 2 O and (GeH 3 ) 2 O compounds our calculated molecular structures and vibrational spectra are in excellent agreement with experiment. The hypothetical SiH 3 OGeH 3 molecule is predicted to possess an intermediate molecular structure and energy, with stability differences on the order of 1-2 kcal/mol between SiH 3 OGeH 3 and mixtures of (SiH 3 ) 2 O/(GeH 3 ) 2 O. For the solids we predict two new ordered structures: (i) an R-SiGeN 2 O phase composed of a uniform distribution of SiN 3 O and GeN 3 O tetrahedra, and (ii) a "pseudo-lamellar" form β-SiGeN 2 O in which the SiN 3 O and GeN 3 O units occupy alternating layers. The structural, electronic, and thermoelastic properties of the latter are then systematically compared to those of Si 2 N 2 O and Ge 2 N 2 O. Here again, small energy differences comparable to those in the molecular case are found between the SiGeN 2 O polytypes and their Si 2 N 2 O/Ge 2 N 2 O analogues. The enthalpy of formation of R-SiGeN 2 O, β-SiGeN 2 O, and a random SiGeN 2 O alloy are predicted to be comparable, indicating that mixing entropy should favor the disordered solid at high temperatures. Collectively, a remarkable consistency is found for the bond-lengths and bond-angles across molecular and solid-state forms. From an experimental perspective, the recent development of industrial scale synthesis for (SiH 3 ) 2 O suggests that the Ge-based analogues proposed here might be accessed using similar approaches, opening the door to new chemically compatible Si-Ge-O-N high-k gate materials for high mobility Si-Ge based applications.

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“…However, solid C 2 N 2 O might be an interesting material in itself because of possible analogies with Si 2 N 2 O, as they have been indicated by some theoretical studies. 19 Experimental details Synthesis 30 g of freshly prepared AgNCO (silver isocyanate) were dried under dynamic vacuum (p ¼ 10 À2 mbar) at T ¼ 80 C for several days. The absence of moisture was checked by infrared spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Cyanogen isocyanate (NC–NCO) revisited: thermal and chemical reactivity of a hydrogen-free precursor to C–N–(O) polymers

Schmidt

Jansen

2010

J. Mater. Chem.

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Ab-initio Calculations of the Electronic Structure and Cohesive Properties of the Orthorhombic Oxynitrides X2N2O (X = C, Si, Ge)

Cited by 9 publications

References 33 publications

Ternary Inorganic Compounds Containing Carbon, Nitrogen, and Oxygen at High Pressures

Ternary Inorganic Compounds Containing Carbon, Nitrogen, and Oxygen at High Pressures

Si−Ge-based Oxynitrides: From Molecules to Solids

Cyanogen isocyanate (NC–NCO) revisited: thermal and chemical reactivity of a hydrogen-free precursor to C–N–(O) polymers

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