This paper uses electronic structure calculations (density functional theory - DFT) to demonstrate that the electrical conductivity of carbon nanotubes can be enhanced by encapsulating a one-dimensional chain of beryllium within the tube.
The computationally intensive calculations are performed with the open source Quantum Espresso software, and provide data for a Boltzmann transport equation treatment of electrical conductivity.
Quantum Espresso is a code which uses MPI, and is written (mostly) in modern Fortran. Input data for the DFT calculations is available, along with reference output data.
DFT calculations are in principle reproducible between different codes, but differences can arise due to poor choice of convergence tolerances, inappropriate use of pseudopotentials and other numerical considerations. An independent validation of the key quantities needed to compute electrical conductivity would be valuable.
In this case we have published our input files for calculating the four quantities needed to parametrise the transport simulations from which we compute the electrical conductivity. These are specifically electronic band structure, phonon dispersions, electron-phonon coupling constants and third derivatives of the force constants. Each in turn in more sensitive to convergence tolerances than the last, and it is the final quantity on which the conclusions of the paper critically depend.
Reference output data is provided for comparison at the data URL below.
We note that the pristine CNT results (dark red line) in figure 3 are an independent reproduction of earlier work and so we are confident the Boltzmann transport simulations are reproducible. The calculated inputs to these from DFT (in the case of Be encapsulation) have not been independently reproduced to our knowledge.
A suggestion would be for the reviewers to reproduce the calculations using the inputs provided at the data URL, and compare these to the reference data provided. These calculations should run over a period of a few days. Testing the sensitivity of these to convergence parameters would be a valuable exercise. Reviewers might then attempt to reproduce figure S1 and figure 2.
Reproducing the Boltzmann transport simulations from the DFT data is likely to be beyond the scope achievable within a ReproHack, but full information on the discretisation scheme used is provided in the SI should reviewers wish to attempt it.
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