Statistical mechanics of monatomic liquids

Journal Article · Wed Oct 01 04:00:00 EDT 1997 · Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics

DOI:https://doi.org/10.1103/PhysRevE.56.4179· OSTI ID:632545

Wallace, D C ^[1]

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1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

Two key experimental properties of elemental liquids, together with an analysis of the condensed-system potential-energy surface, lead us logically to the dynamical theory of monatomic liquids. Experimentally, the ion motional specific heat is approximately 3Nk for N ions, implying the normal modes of motion are approximately 3N independent harmonic oscillators. This implies the potential surface contains nearly harmonic valleys. The equilibrium configuration at the bottom of each valley is a {open_quotes}structure.{close_quotes} Structures are crystalline or amorphous, and amorphous structures can have a remnant of local crystal symmetry, or can be random. The random structures are by far the most numerous, and hence dominate the statistical mechanics of the liquid state, and their macroscopic properties are uniform over the structure class, for large-N systems. The Hamiltonian for any structural valley is the static structure potential, a sum of harmonic normal modes, and an anharmonic correction. Again from experiment, the constant-density entropy of melting contains a universal disordering contribution of Nk{Delta}, suggesting the random structural valleys are of universal number w{sup N}, where lnw={Delta}. Our experimental estimate for {Delta} is 0.80. In quasiharmonic approximation, the liquid theory for entropy agrees with experiment, for all currently analyzable experimental data at elevated temperatures, to within 1{endash}2{percent} of the total entropy. Further testable predictions of the theory are mentioned. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 632545
• Journal Information: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Journal Name: Physical Review. E, Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics Journal Issue: 4 Vol. 56; ISSN PLEEE8; ISSN 1063-651X
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
AMORPHOUS STATE
CRYSTALS
DENSITY
ENTROPY
EQUILIBRIUM
HAMILTONIANS
HARMONIC OSCILLATORS
LIQUIDS
MELTING
POTENTIAL ENERGY
SPECIFIC HEAT
STATISTICAL MECHANICS
SURFACES