Pressure-induced tetrahedral tilting and deformation in Ge<sub>2</sub>N<sub>2</sub>O

Srinivasa, S. R.; Cartz, L.; Jorgensen, J. D.; Labbé, Jean‐Claude

doi:10.1107/s0021889879013182

Cited by 10 publications

(12 citation statements)

References 7 publications

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“…However, the corresponding bulk modulus derivative values for all of our simulated structures is also in this range ( B 0 ′ ∼ 0.5−1.5), suggesting that this may be a characteristic value for these materials and not an experimental artifact. The compressibility of Ge 2 N 2 O has also been determined experimentally to be ∼101 GPa, which is somewhat higher than our theoretical value of 91 GPa. The origin of the discrepancy is likely related to inaccuracies associated with the severely limited compression range ( P < 3 GPa) used in their experiment …”

Section: Properties Of Solid State Si2n2o Ge2n2o and Sigen2ocontrasting

confidence: 70%

“…The compressibility of Ge 2 N 2 O has also been determined experimentally to be ∼101 GPa, which is somewhat higher than our theoretical value of 91 GPa. The origin of the discrepancy is likely related to inaccuracies associated with the severely limited compression range ( P < 3 GPa) used in their experiment …”

Section: Properties Of Solid State Si2n2o Ge2n2o and Sigen2ocontrasting

confidence: 70%

“…The origin of the discrepancy is likely related to inaccuracies associated with the severely limited compression range (P < 3 GPa) used in their experiment. 26 Also listed in Table 7 are the "Vegard average" EOS parameters of Si 2 N 2 O and Ge 2 N 2 O, which correspond closely to those of R-SiGeN 2 O and β-SiGeN 2 O. We note, however, that while the energy and volume of the R-and β-are very similar, the bulk modulus of β-SiGeN 2 O (118 GPa) is ∼9.5% larger than that of the R-SiGeN 2 O phase (108 GPa).…”

Section: Molecular Properties Of Gasmentioning

confidence: 99%

“…Over the pressure range -10 to 25 GPa the volume change in all four compounds is found to be directly correlated with the tilting of the SiN 3 O/GeN 3 O tetrahedra, as suggested by the prior experimental studies of Srinisvasa and co-workers. 26 Finally, we note from the static lattice equilibrium (electronic) energies in Table 7 that the R-SiGeN 2 O and β-SiGe-N 2 O phases are marginally metastable with respect to an equivalent stoichiometric mixture of Si 2 N 2 O and Ge 2 N 2 O. Using the EOS fit data it is trivial to construct the enthalpy functions for the relevant phases to examine the phase stability of the R-and β-polytypes as a function of pressure.…”

Section: Molecular Properties Of Gasmentioning

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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Section: Properties Of Solid State Si2n2o Ge2n2o and Sigen2ocontrasting

confidence: 70%

Section: Properties Of Solid State Si2n2o Ge2n2o and Sigen2ocontrasting

confidence: 70%

Section: Molecular Properties Of Gasmentioning

confidence: 99%

Section: Molecular Properties Of Gasmentioning

confidence: 99%