MedeA® Phonon: Capturing "Relevant Temperatures"

Before scientists and engineers had today’s computing power, it was often a Herculean effort to capture “relevant temperatures” in modeling scenarios. Our Phonon module takes advantage of technology and our computational materials science expertise to compute temperature-dependent vibrational properties of solids, surfaces, interfaces, molecules and clusters. This provides critical insight into temperature dependent effects.

MedeA-Phonon is based on the PHONON program authored by Prof. Krzysztof Parlinski. The only input required are optimized crystal structures and atomic forces, as computed from ab initio techniques such as VASP for a majority of applications, but also semiempirical quantum (MedeA-MOPAC) and forcefield methods (MedeA-LAMMPS) can be applied. Phonon is extremely well tested, and proven to provide accurate results for a wide range of materials. 

MedeA Phonon: Capturing "Relevant Temperatures"

Key Benefits of Phonon

  • Ability to describe systems at finite temperatures
  • Predicts materials behavior over a wide temperature range
  • Use Phonon to determine phase stability, soft modes and predict displacive phase transitions to lower symmetry phases
  • Computes temperature dependent heat capacity, enthalpy, entropy and free energy
  • Describes vibrational modes of interfacial atoms, surfaces and molecules on surfaces
  • Helps with interpretation in Infrared and Raman spectroscopy
  • Handles hundreds of calculations through JobServer/TaskServer

Properties from Phonon module

  • Phonon dispersion relations
  • Animation of vibrations for any phonon modes
  • Total and partial phonon density of states
  • Zero point energy
  • Thermodynamical funtions: Vibrational part of heat capacity, enthalpy, entropy, and free energy as a function of temperature
  • Electronic contribution to the free energy from Fermi occupation
  • Classification of vibrational modes at the zone center: Infrared and Raman active or silent modes
  • Infrared and Raman spectra including intensities and separation of TO and LO components

Computational characteristics

  • Automatic detection and use of any space-group symmetry
  • Fully automatic determination of supercell and all necessary atomic displacements
  • Fully automated setup, execution, and processing of VASP jobs
  • Automatic coverage of LO-TO mode split at the zone center
  • Uses forces computed with VASP 5.4 by any of the functionals available. This includes the ability to use GGA+U and hybrid functionals, spin-polarization and fully relativistic Hamiltonians
  • Partial freezing of atoms possible, e.g. to selectively obtain vibrational modes of molecules on surfaces at moderate computational cost
  • Applicable to transition state geometries to obtain vibrational partition functions for the calculation of reaction and diffusion rates within Eyring’s transition state theory
  • Restart capabilities in case of hardware or communication failures (larger systems may involve several hundred individual tasks, which are controlled automatically by the JobServer)

Required MedeA® modules

Original reports

  • K. Parlinski, Z. Q. Li, and Y. Kawazoe, First-Principles Determination of the Soft Mode in Cubic ZrO2, Phys. Rev. Lett. 78, 4063 (1997).
  • Krzysztof Parlinski PHONON Manual, ver. 1.04, Cracow, 1998. ver. 6.15, Cracow, 2014.