Thermodynamic, dynamic and structural properties of liquid and supercritical matter
Abstract
Among three basic states of matter (solid, liquid, gas), liquids are least understood
from the theoretical point of view. The perceived diffculty is that interactions in a liquid
are both strong and system-specific, implying that the energy strongly depends on the
liquid type and that, therefore, liquid energy can not be calculated in general form.
In this thesis, a phonon theory of liquids is developed where this problem is avoided.
Central to the thesis is a development an alternative to calculating liquid energy and
heat capacity. The proposed phonon theory of liquids covers both classical and quantum
regimes and accounts for the contribution of anharmonicity and thermal expansion to
liquid energy and heat capacity. Within the framework of the phonon theory of liquids
a good agreement of calculated and experimental heat capacity of liquids, including
helium, noble, metallic, molecular and hydrogen-bonded network liquids in a wide range
of temperature and pressure is demonstrated.
It was also found that in the very wide pressure range 5 MPa-500 MPa liquid helium
near melting temperature is both solid-like and quantum.
The thermodynamic properties of the supercritical state are studied, which lead to
discovery that specific heat shows a crossover between two different dynamic regimes of
the low-temperature rigid liquid and high-temperature non-rigid supercritical
fluid. A
theory of heat capacity above the crossover is formulated, and good agreement between
calculated and experimental data for rare-gas supercritical liquids is obtained. The
relationship between power exponents of heat capacity and viscosity in the supercritical
region is derived. The thermodynamic properties are explained by the temperature
behaviour of the maximal length of the longitudinal phonons that can exist in the
supercritical system and that is not sensitive to system details.
We also introduce a new idea that enables a unified description of all three states of
matter. A generic form of an interacting phonon Hamiltonian with ground state configurations
minimising the potential is introduced. Symmetry breaking leads to emergence
of energy gaps of shear excitations as a consequence of the Goldstone theorem, and
readily results in the emergence of energy spectra of solid, liquid and gas phases.
Authors
Bolmatov, DmitryCollections
- Theses [3831]