First principle (or ab initio) thermodynamics and transport

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First-principle (or ab initio) thermodynamics

Most materials are composed of a several chemical species. In the bulk, these materials possess a fixed stoichiometry, for example, A2B3C4 etc. At surfaces and interfaces, there is room for stoichiometric variations, in particular, there can be an excess or a deficiency (with respect to the bulk stoichiometry) of one or more chemical species.
The stability and physical properties of surfaces and interfaces can depend strongly on their detailed chemical composition (and the associated atomic structure). Identification of relevant compositions of these systems requires a thermodynamic treatment.

We distinguish the following two situations:

  • Composition of surfaces in equilibrium with a surrounding:
    here it is possible with an adaptation of AIT-SE

  • Composition of surfaces, interfaces and thin-films as they aris in a (nonequilibrium) deposition process from a gas phase:
    here a new nonequilibrium method, called AIT-DG, is essential to capture dependence of the environment.

    Nonequilibrium account of the deposition conditions

    Description of rate-equation modelling: under construction.

    Summary of first-principle thermodynamics results

    Failure of equilibrium predictions for wear-resistant coatings

    J Rohrer, C Ruberto, and P Hyldgaard,
    "Ab initio structure modelling of complex thin-film oxides: thermodynamical stability of TiC/thin-film alumina",
    J. Phys.: Condens. Matter 22 015004 (2010), see also cond-mat/0903.1252.

    Development of AIT-DG and application to as-grown coatings

    J Rohrer and P Hyldgaard,
    "Ab-initio thermodynamics of deposition growth: surface terminations of CVD titanium carbide and nitride",
    Phys. Rev. B 82, 045415 (2010), see also cond-mat/1004.1929.

    J Rohrer and P Hyldgaard,
    "Understanding adhesion at as-deposited interfaces from ab initio thermodynamics of deposition growth: thin-film alumina on titanium carbide",
    J. Phys.: Condens. Matter, 22, 472001 (2010). Fast track publication.
    Copyright (2010) by IoP.
    Included on IoP Select.

    First-principle thermodynamics of tunneling transport

    Nonequilibrium account of interacting tunneling

    Description of partition-free tunneling as a formal collision problem: under construction.

    Summary of formally exact transport and thermodynamics descriptions

    A Uniqueness of density and variational T-matrix formulation

    P. Hyldgaard,
    Density-functional theory of nonequilibrium tunneling,
    Phys. Rev. B 78, 165109 (2008).
    Copyright (2008) by the American Physical Society.

    Varitaional ab initio thermoydnamics, adiabatic forces and a nonequilibrium Born-Oppenheimer approximation

    P. Hyldgaard,
    Nonequilibrium thermodynamics of interacting tunneling transport: variational grand potential, universal density functional description, and nature of forces,
    J. Phys.:Condens. Matter 24, 424219 (2012).