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Investigating finite-size effects in computer simulations of superionic materials

Federico Grasselli1*

1 Laboratory of Computational Science and Modelling (COSMO), IMX, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland

* Corresponding authors emails: federico.grasselli@epfl.ch
DOI10.24435/materialscloud:jy-tw [version v1]

Publication date: Feb 04, 2022

How to cite this record

Federico Grasselli, Investigating finite-size effects in computer simulations of superionic materials, Materials Cloud Archive 2022.22 (2022), doi: 10.24435/materialscloud:jy-tw.

Description

The effects of the finite size of the simulation box in equilibrium molecular dynamics simulations are investigated for prototypical superionic conductors of different types, namely the fluorite-structure materials PbF2, CaF2, and UO2 (type II), and the alpha phase of AgI (type I). Largely validated empirical force-fields are employed to run ns-long simulations and extract general trends for several properties, at increasing size and in a wide temperature range. This work shows that, for the considered type-II superionic conductors, the diffusivity dramatically depend on the system size and that the superionic regime is shifted to larger temperatures in smaller cells. Furthermore, only simulations of several hundred atoms are able to capture the experimentally-observed, characteristic change in the activation energy of the diffusion process, occurring at the order-disorder transition to the superionic regime. Finite-size effects on ion diffusion are instead much weaker in alpha-AgI. The thermal conductivity is found generally smaller for smaller cells, where the temperature-independent (Allen-Feldman) regime is also reached at significantly lower temperatures. The finite-size effects on the thermal motion of the non-mobile ions composing the solid matrix follow the simple law which holds for solids. In this record, I collect the input files employed to run the simulations, the data obtained from the latter and the Jupiter Notebook used to analyze the data.

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Files

File name Size Description
alpha-AgI.zip
MD5md5:6532ccd122eaf453975676e0e8acbbc0
572.8 MiB Zipped directory containing inputs and results of the LAMMPS simulation of alpha-AgI at different temperatures and system sizes
Argon.zip
MD5md5:c44a397ee8c781cb958d1cf69309fa43
861.7 KiB Zipped directory containing inputs and results of the LAMMPS simulation of FCC argon at different temperatures and system sizes
CaF2.zip
MD5md5:7a88bad620f87627aa4acb18266254d1
767.7 MiB Zipped directory containing inputs and results of the LAMMPS simulation of CaF2 at different temperatures and system sizes
PbF2.zip
MD5md5:7c99d63a2e0e0662a2aa634496405e39
1.1 GiB Zipped directory containing inputs and results of the LAMMPS simulation of PbF2 at different temperatures and system sizes
PbF2_XM.zip
MD5md5:c9f7d63182336574c0642c273661d5bb
117.8 MiB Zipped directory containing inputs and results of the LAMMPS simulation of PbF2 at different temperatures and system sizes, with modified masses
UO2.zip
MD5md5:ba43b29a5c7308bcca86b29041c559a6
302.6 MiB Zipped directory containing inputs and results of the LAMMPS simulation of UO2 at different temperatures and system sizes
UO2_heat.zip
MD5md5:de844afbecd3fd5e72812ccb341644ad
1007.8 MiB Zipped directory containing inputs and results of the LAMMPS simulation of heat transport in UO2 at different temperatures and system sizes
thermocepstrum-develop.zip
MD5md5:bf2003a64fd5e50f8685fad34a250403
12.0 MiB SportTran-Thermocepstrum version employed in the analysis of thermal transport from simulations
analisi.zip
MD5md5:663f180060c121cc92661b3333c9790e
256.6 MiB ANALISI - code employed to perform the calculation of diffusion coefficient. Instructions on compilation and use are provided in the main directory
lammps-stable.tar.gz
MD5md5:baff854c3e4d62df6fc6f86c8f6fe87b
164.8 MiB LAMMPS version employed in the simulations
NOTEBOOK_MC_FSE_SI.ipynb
MD5md5:5c6b2677443faad88e4b2ed5b4053262
11.4 MiB Jupyter Notebook employed to analyze the data. The directories containing the data (uploaded in this record) must be unzipped and the Jupyter notebook must be run in their parent directory. Simulations shall be thus accessed with the default path used inside the notebook; in this way, for instance, "./PbF2/NVE_L_T_6p056_heat/" specifies the set of NVE simulations of heat transport of PbF2 at 6.056 angstrom lattice.
README.txt
MD5md5:c5033d0eecaeafeb96f4429002c93d0e
1.5 KiB README file a more extensive description of the data.

License

Files and data are licensed under the terms of the following license: Creative Commons Attribution 4.0 International.
Metadata, except for email addresses, are licensed under the Creative Commons Attribution Share-Alike 4.0 International license.

External references

Preprint (Preprint where the data is discussed)
F. Grasselli, arXiv (2022), (in preparation)

Keywords

Marie Curie Fellowship H2020 molecular dynamics simulation transport

Version history:

2022.22 (version v1) [This version] Feb 04, 2022 DOI10.24435/materialscloud:jy-tw