Description

As we push the boundaries of space exploration with new missions to nearby planets, improving our investigation tools is crucial. Mars rovers have revealed a surface mineralogy unlike anything on Earth, shaped by the planet’s former hydrosphere followed by an extended dry and cold environment. For example, this favors the formation of perchlorates, or mixed silicate–salts glassy phases — minerals that are difficult to synthesize and stabilize on Earth but remain surprisingly stable on Mars. Recent Raman spectrometry data confirms their presence, highlighting an opportunity for deeper research. Understanding these minerals could offer new insights into Martian chemistry and planetary evolution.
Here we want to calculate the theoretical Raman spectra of perchlorates and other Martian minerals using the density functional perturbation theory (DFPT) as implemented in the ABINIT package. We want to obtain not only the position and the intensity of the peaks, but also the peak widths. They are necessary to correctly identify between similar spectra and to assess, by integration, the actual intensity of the peaks, which are directly comparable to experimental values on the field. These allow us to choose the representative peaks that can be used in identification and to analyze the displacement patterns associated with the vibrations. The results of our simulations will be compared and interpreted in the light of measurements performed by the current rovers on the surface of Mars.
For this, we need to implement several third- and fourth-order derivatives of the energy. This will be done as a series of DFPT terms, where the perturbations can be atomic displacements or electric fields. We will use a combination of the 2n+1 theorem and finite differences. The implementation will be done within the 'Projector Augmented-Wave' approach (PAW) to DFT. The entire development effort will be integrated into the ABINIT package and made available to the entire community. ABINIT (www.abinit.org) is a highly visible international collaborative project for ab initio simulations based on DFT and DFPT. The computed spectra will be made available to the community via the WURM database.
The successful candidate will be co-advised between the IPGP (Paris) and the CEA (Bruyères-le-Chatel, S of Paris) groups. IPGP is a world-renowned geosciences research institute founded in 1921, associated with the CNRS, a component of the Université Paris Cité and employing more than 500 people. The group of Razvan Caracas is highly active in computational mineralogy, study of matter at extreme conditions, and planetology. The Quantum simulation of Matter group at CEA Bruyères-le-Chatel led by Marc Torrent is a main developer of the ABINIT package, highly active in density functional theory, projector augmented-wave, and high-performance computing.

Skills required

Advanced computing skills in high-level languages, like Python, and in C++ or Fortran, and solid knowledge of condensed matter physics and chemistry, including density functional theory.

Bibliography

https://www.abinit.org
https://wurm.info
Gonze, X. et al., “Recent developments in the ABINIT software package: Response-function capabilities and beyond”, J. Chem. Phys. 152, 124102 (2020)
Gonze, X., “Dynamical matrices, born effective charges, dielectric permittivity tensors, and interatomic force constants from density-functional perturbation theory”, Physical Review. B 55, 10355(1997)
Raman spectra via DFPT
Caracas, R. & R. E.Cohen (2006), 'Theoretical determination of the Raman spectra of MgSiO3 perovskite and post-perovskite at high pressure', Geophys. Res. Lett., 33, L12S05
Torrent, M. et al., “Implementation of the projector augmented-wave method in the ABINIT code: Application to the study of iron under pressure”, Computational Materials Science 42, 337 (2008)
Miwa K., 'Prediction of Raman spectra with ultrasoft pseudopotentials', Phys. Rev. B 84, 094304 (2011)

Keywords

Solid-state physics, Spectroscopy, Numerical simulation, Quantum physics, Minerals