First Principle Free Energy Calculations Made Simple: The Example Case of Alanine Dipeptide, from Classical Force-field to Hybrid Functional.

ORAL

Abstract

Ab initio molecular dynamics (AIMD) is a powerful method to study the microscopic properties of broad classes of materials, but its predictive power is limited by the short timescales that can be investigated. Here, we present a scheme coupling SSAGES1, a plug-in for enhanced sampling calculations, and Qbox2, a plane-wave DFT MD code, that allows for the efficient use of several enhanced sampling techniques in AIMD. We demonstrate the power of the framework by computing the free energy surface (FES) of alanine-dipeptide in vacuum with Adaptive-Bias-Force using classical potentials and two density functionals: a semi-local (PBE) and a hybrid functional (PBE0). We find substantial differences between the results of DFT and those of the classical potentials: the latter accurately reproduce the energy minima of the system, however, they describe inaccurately high free energy states. The coupling scheme introduced here is general and allows for simple and straightforward calculations of FES from first principles.

1 http://miccomcodes.org/manual/index.html
2 http://qboxcode.org

*This work was supported by MICCoM, as part of the Computational Materials Sciences Program funded by the DOE. The work of H.S. was supported by the Graduate Research Fellowship Program of the NSF.

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Presenters

  • Federico Giberti

    • Institute for Molecular Engineering, University of Chicago
    • Institute for Molecular Engineering, Univ of Chicago

Authors

  • Emre Sevgen

    • Institute for Molecular Engineering, Univ of Chicago

  • Federico Giberti

    • Institute for Molecular Engineering, University of Chicago
    • Institute for Molecular Engineering, Univ of Chicago

  • Hythem Sidky

    • Chemical and Biomolecular Engineering, University of Notre Dame
    • Univ of Notre Dame
    • Department of Chemical and Biomolecular Engineering, University of Notre Dame

  • Jonathan Whitmer

    • Chemical & Biomolecular Engineering, University of Notre Dame
    • Chemical and Biomolecular Engineering, University of Notre Dame
    • Univ of Notre Dame
    • Department of Chemical and Biomolecular Engineering, University of Notre Dame

  • Giulia Galli

    • Institute for Molecular Engineering, University of Chicago
    • Univ of Chicago
    • University of Chicago
    • Institute for Molecular Engineering, University of Chicago; Argonne National Laboratory
    • Institute for Molecular Engineering, University of Chicago, Chicago, IL, United States and Materials Science Division, Argonne National Laboratory
    • University of Chicago; Argonne National Laboratory
    • Institute for Molecular Engineering, Univ of Chicago

  • Francois Gygi

    • Department of Computer Science, University of California Davis
    • University of California, Davis
    • Univ of California - Davis

  • Juan De Pablo

    • Institute for Molecular Engineering, The University of Chicago
    • Institute for Molecular Engineering, Univ of Chicago
    • Institute for molecular engineering, The University of Chicago
    • University of Chicago
    • Univ of Chicago
    • Institute for Molecular Engineering, University of Chicago
    • The Institute for Molecular Engineering, The University of Chicago
    • Institute of Molecular Engineering, University of Chicago