scholarly journals Density-functional studies of high-pressure properties and molecular dissociations of halogen molecular crystals

2003 ◽  
Vol 68 (9) ◽  
Author(s):  
M. S. Miao ◽  
V. E. Van Doren ◽  
José Luís Martins
Keyword(s):  
High Pressure ◽  
Density Functional ◽  
Molecular Crystals ◽  
Functional Studies

scholarly journals High pressure ionic and molecular crystals of ammonia monohydrate within density functional theory

2012 ◽  
Vol 137 (6) ◽  
pp. 064506 ◽  
Author(s):  
Gareth I.G. Griffiths ◽  
Alston J. Misquitta ◽  
A. Dominic Fortes ◽  
Chris J. Pickard ◽  
Richard J. Needs
Keyword(s):  
Density Functional Theory ◽  
High Pressure ◽  
Density Functional ◽  
Molecular Crystals ◽  
Functional Theory

scholarly journals Compressibility and Phase Stability of Iron-Rich Ankerite

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 607
Author(s):  
Raquel Chuliá-Jordán ◽  
David Santamaria-Perez ◽  
Javier Ruiz-Fuertes ◽  
Alberto Otero-de-la-Roza ◽  
Catalin Popescu
Keyword(s):  
High Pressure ◽  
Density Functional ◽  
Computational Study ◽  
Density Functional Theory Calculations ◽  
High Pressure Phase ◽  
Stable Phase ◽  
Pressure Derivative ◽  
Reversible Phase Transition ◽  
Murnaghan Equation ◽  
Pressure Phase

The structure of the naturally occurring, iron-rich mineral Ca1.08(6)Mg0.24(2)Fe0.64(4)Mn0.04(1)(CO3)2 ankerite was studied in a joint experimental and computational study. Synchrotron X-ray powder diffraction measurements up to 20 GPa were complemented by density functional theory calculations. The rhombohedral ankerite structure is stable under compression up to 12 GPa. A third-order Birch–Murnaghan equation of state yields V0 = 328.2(3) Å3, bulk modulus B0 = 89(4) GPa, and its first-pressure derivative B’0 = 5.3(8)—values which are in good agreement with those obtained in our calculations for an ideal CaFe(CO3)2 ankerite composition. At 12 GPa, the iron-rich ankerite structure undergoes a reversible phase transition that could be a consequence of increasingly non-hydrostatic conditions above 10 GPa. The high-pressure phase could not be characterized. DFT calculations were used to explore the relative stability of several potential high-pressure phases (dolomite-II-, dolomite-III- and dolomite-V-type structures), and suggest that the dolomite-V phase is the thermodynamically stable phase above 5 GPa. A novel high-pressure polymorph more stable than the dolomite-III-type phase for ideal CaFe(CO3)2 ankerite was also proposed. This high-pressure phase consists of Fe and Ca atoms in sevenfold and ninefold coordination, respectively, while carbonate groups remain in a trigonal planar configuration. This phase could be a candidate structure for dense carbonates in other compositional systems.

scholarly journals Calculation and interpretation of classical turning surfaces in solids

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Aaron D. Kaplan ◽  
Stewart J. Clark ◽  
Kieron Burke ◽  
John P. Perdew
Keyword(s):  
Density Functional ◽  
Molecular Crystals ◽  
Chemical Properties ◽  
Density Functionals ◽  
Compression And Expansion ◽  
Forbidden Regions ◽  
Internuclear Distances ◽  
Wide Gap ◽  
Equilibrium Geometries ◽  
Classical Picture

AbstractClassical turning surfaces of Kohn–Sham potentials separate classically allowed regions (CARs) from classically forbidden regions (CFRs). They are useful for understanding many chemical properties of molecules but need not exist in solids, where the density never decays to zero. At equilibrium geometries, we find that CFRs are absent in perfect metals, rare in covalent semiconductors at equilibrium, but common in ionic and molecular crystals. In all materials, CFRs appear or grow as the internuclear distances are uniformly expanded. They can also appear at a monovacancy in a metal. Calculations with several approximate density functionals and codes confirm these behaviors. A classical picture of conduction suggests that CARs should be connected in metals, and disconnected in wide-gap insulators, and is confirmed in the limits of extreme compression and expansion. Surprisingly, many semiconductors have no CFR at equilibrium, a key finding for density functional construction. Nonetheless, a strong correlation with insulating behavior can still be inferred. Moreover, equilibrium bond lengths for all cases can be estimated from the bond type and the sum of the classical turning radii of the free atoms or ions.

Density functional studies on the adsorption and decomposition of SO2 on Cu(100)

2001 ◽  
Vol 115 (1) ◽  
pp. 454-465 ◽  
Author(s):  
José A. Rodriguez ◽  
Josep M. Ricart ◽  
Anna Clotet ◽  
Francesc Illas
Keyword(s):  
Density Functional ◽  
Functional Studies
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