Crystals from first principles

Maddox, John

doi:10.1038/335201a0

Cited by 400 publications

(258 citation statements)

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“…Finding thermodynamically stable structures for solids of given stoichiometry is a notoriously difficult task (13), which remains true even for transitions between ground state structures, as considered in what follows. When chemical intuition (14) fails one possible method to effectively and efficiently sample the configurational space of solid state structures for a given stoichiometry utilizes genetic or evolutionary algorithms.…”

Section: Searching Methodologymentioning

confidence: 99%

High pressure ices

Hermann

Ashcroft

Hoffmann

2011

Proc. Natl. Acad. Sci. U.S.A.

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H 2 O will be more resistant to metallization than previously thought. From computational evolutionary structure searches, we find a sequence of new stable and meta-stable structures for the ground state of ice in the 1-5 TPa (10 to 50 Mbar) regime, in the static approximation. The previously proposed Pbcm structure is superseded by a Pmc2 1 phase at p ¼ 930 GPa, followed by a predicted transition to a P2 1 crystal structure at p ¼ 1.3 TPa. This phase, featuring higher coordination at O and H, is stable over a wide pressure range, reaching 4.8 TPa. We analyze carefully the geometrical changes in the calculated structures, especially the buckling at the H in O-H-O motifs. All structures are insulatingchemistry burns a deep and (with pressure increase) lasting hole in the density of states near the highest occupied electronic levels of what might be component metallic lattices. Metallization of ice in our calculations occurs only near 4.8 TPa, where the metallic C2∕m phase becomes most stable. In this regime, zero-point energies much larger than typical enthalpy differences suggest possible melting of the H sublattice, or even the entire crystal.hydrogen bonds | compressed water

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Section: Searching Methodologymentioning

confidence: 99%

High pressure ices

Hermann

Ashcroft

Hoffmann

2011

Proc. Natl. Acad. Sci. U.S.A.

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“…Therefore, knowledge not only of average liquid configurations but also of the solid mixture's structure is essential. For phase transitions of mixtures, the problem is hence strongly linked to the challenge of predicting molecular crystals from first principles [12], which has been addressed for co-crystals only recently [7,13] in mapping out entire phase diagrams. For the identification of HTF mixtures with minimal melting points, however, it is sufficient to simply focus on eutectics, rather than having to screen the entire solid-liquid phase diagram.…”

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confidence: 99%

“…Therefore, knowledge not only of average liquid configurations but also of the solid mixture's structure is essential. For phase transitions of mixtures, the problem is hence strongly linked to the challenge of predicting molecular crystals from first principles [12], which has been addressed for co-crystals only recently [7,13]. Recent efforts to compute solid-liquid phase equilibria of hard sphere mixtures [14], Lennard-Jones mixtures [15], alloys [16], or solid and liquid mixtures of the Rb/Cs fluoride binary [17] in mapping out entire phase diagrams.…”

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confidence: 99%

Molten salt eutectics from atomistic simulations

2011

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Despite their importance for solar thermal power applications, phase-diagrams of molten salt mixture heat transfer fluids (HTFs) are not readily accessible from first principles. We present a molecular dynamics scheme general enough to identify eutectics of any HTF candidate mixture. The eutectic mixture and temperature are located using the liquid mixture free energy and the pure component solid-liquid free energy differences. The liquid mixture free energy is obtained using thermodynamic integration over particle identity transmutations sampled with molecular dynamics at a single temperature. According to Carnot's cycle, the maximum efficiency of solar thermal power facilities increases with the temperature difference between melting and thermal decomposition of employed heat transfer fluids (HTFs). Consequently, new formulations of low melting but temperature resistant molten salt mixtures are actively sought [1]. Competitive formulations currently include eutectics of alkali and alkali-metal earth nitrates and nitrite mixtures. Unfortunately, the dimensionality of the combinatorial multicomponent space of all possible cations and anions prohibits exhaustive scanning using computer simulation. Once an optimal HTF formulation is identified, however, its realization through simple mixing is readily accomplished in experiment. Identifying new HTFs therefore represents a rewarding challenge for atomistic first principles materials design efforts using theory and computation. Ab initio (AI) based design, through an efficient combination of first principles methods and optimization algorithms [2], has already been applied to inverting band structures [3], identifying stable alloys [4], designing heterogeneous catalysts [5,6], or discovering ternary metal oxides for batteries [7]. Identity transformations, also called "alchemical" transmutations [8], have been successfully applied to compute compositions in the earth's core [9], phase stability in solid solutions [10], and a wide variety of biochemical applications [11], among others.The Gibbs criteria for phase equilibrium dictates that temperature, pressure, and chemical potential of individual components must be equal in coexisting phases. Therefore, knowledge not only of average liquid configurations but also of the solid mixture's structure is essential. For phase transitions of mixtures, the problem is hence strongly linked to the challenge of predicting molecular crystals from first principles [12], which has been addressed for co-crystals only recently [7,13] in mapping out entire phase diagrams. For the identification of HTF mixtures with minimal melting points, however, it is sufficient to simply focus on eutectics, rather than having to screen the entire solid-liquid phase diagram. Here, we present a first principles approach for directly estimating eutectic compositions and temperatures for any number of components, relying on a combination of only a couple of molecular dynamics (MD) calculations per mole fraction at a single temperature and knowledge ab...

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“…The limitation to date has largely been computational cost, but this is changing quickly; further investigation of the transition from clusters to bulk-like nanoparticles will undoubtedly shed significant light on fundamental questions, such as how the structures of crystalline solids emerge from the properties of a collection of atoms, which remains only poorly understood [97,98].…”

Section: Extreme and Limiting Casesmentioning

confidence: 99%

Cluster melting: new, limiting, and liminal phenomena

Gaston

2018

Advances in Physics: X

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The thermodynamic behaviour of clusters and nanoscale structures is both a challenge to the statistical basis of the theory, and of paramount importance to experiment. In this review, the competing influences that determine the melting temperature and behaviour of small atomic clusters is discussed, with reference to both experiment and theory. The liminal spaces between solid and liquid, the non-scaling and scaling regimes, and the metallic and non-metallic states are discussed, and presented as a primary cause of the emergence of new phenomena. Particular emphasis is given to recent theoretical work that combines each of these liminal regions and enables, through first principles calculations of dynamic atomic interactions in Born Oppenheimer molecular dynamics, the explanation of greater than bulk melting temperatures in certain atomic cluster systems. Some perspective is also given on the important questions in nanoscale thermodynamics that remain to be addressed. ARTICLE HISTORY

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Crystals from first principles

Cited by 400 publications

References 0 publications

High pressure ices

High pressure ices

Molten salt eutectics from atomistic simulations

Cluster melting: new, limiting, and liminal phenomena

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