These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: First-principles lattice dynamics calculations of the phase boundary between beta-Si3N4 and gamma-Si3N4 at elevated temperatures and pressures.
    Author: Togo A, Kroll P.
    Journal: J Comput Chem; 2008 Oct; 29(13):2255-9. PubMed ID: 18548525.
    Abstract:
    The phase boundary between beta-Si(3)N(4) and gamma-Si(3)N(4) is investigated at high pressure and high temperature using first-principles lattice dynamics calculations within the quasi-harmonic approximation. We find a positive slope of the phase boundary, hence, at higher temperatures it requires higher pressures to synthesize the high-pressure polymorph of silicon nitride. It turns out that the thermal expansion of the spinel-type gamma-phase is larger than that of the phenacite-type beta-phase. On the other side, pressure affects more the volume of beta-Si(3)N(4) than of gamma-Si(3)N(4), reflected in the higher bulk modulus of gamma-Si(3)N(4) up to about 40 GPa. The origin of the different temperature behavior of these phases, consequently, is rooted in a larger volume dependence of the zero point energy in gamma-Si(3)N(4) in comparison to beta-Si(3)N(4).
    [Abstract] [Full Text] [Related] [New Search]