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Displaying 76 - 86 of 86

Order-Disorder Phenomena and Phase Separation

January 1, 2001

Author(s)

Benjamin P. Burton

Order-disorder and phase separation in condensed solutions of two or more components are similar processes that are typically driven by energetics of opposite sign. The components may be: different atomic species in alloys or solid solutions; atoms and

Phonons and Static Dielectric Constant in CaTiO 3 From First Principles

August 1, 2000

Author(s)

Eric J. Cockayne, Benjamin P. Burton

CaTiO 3 has a static dielectric constant that extrapolates to a value greater than 300 at zero temperature. We investigate the origin of this large dielectric response on a microscopic level, using first-principles plane-wave pseudopotential density

Long-Range vs. Short-Range Interactions and the Configurational Energies of Ba(B,B')O 3 and PB(B,B')O 3 Perovskites

May 1, 2000

Author(s)

Benjamin P. Burton

Total energy calculations were performed for three perovskite related ordered supercells in several stoichiometries of A(B,B')O 3; where A = Pb 2+, Ba 2+ and B = Mg 2+ Zn 2+, Sc 3+, In 3+ and B' = Nb 5+, Ta 5+, W 6+. A striking difference between the Pb-

Why Pb(B 1/3 B' (2/3) ) O 3 Perovskites Disorder More Easily than Ba(B 1/3 B' (2/3) ) O 3 Perovskites and the Thermodynamics of (1:1)-Type Short-Range Order in PMN

February 1, 2000

Author(s)

Benjamin P. Burton

Fully relaxed, planewave pseudopotential calculations of formation energies (δE) were performed for ordered supercells in the perovskite based system (1 - X) PbNbO 3 - (X).PbMgO 3, including six different supercells at the X = 1/3 composition [Pb(Mg 1/3Nb

Why Pb(B,B')O 3 Perovskites Disorder at Lower Temperatures than Ba(B,B')O 3 Perovskites

November 1, 1999

Author(s)

Benjamin P. Burton, Eric J. Cockayne

Fully relaxed, planewave pseudopotential calculations of total energies were performed for three ordered perovskite related supercells in each of the eight different stoichiometries of A(B 1/3B' 2/3)O 3; A=Pb, Ba and B=Zn, Mg and B' = Nb, Ta; and the four

Simple Empirical Cluster Expansion Hamiltonians for Modeling Cation Order-Disorder in A(B'^d1/3B2/3)O3 Perovskites Such as Pb(Mg1/3Nb2/3)O3

January 15, 1999

Author(s)

Benjamin P. Burton

Brute force exploration of the simple cubic effective cluster interaction space indicates that linear triplet interaction is both necessary and sufficient to stablizde a P3ml ground state, and a P3ml Fm - 3m transition at 4.5183

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