#README#

This data supports the publication titled
"Fifth-degree elastic energy for predictive continuum stress-strain relations and elastic instabilities under large strain and complex loading in silicon",
authored by
Hao Chen, Nikolai A. Zarkevich, Valery I. Levitas, Duane D. Johnson and Xiancheng Zhang.
Please cite the publication if you use this data.

Data from publication 
"https://doi.org/10.25380/iastate.7125368" is used.  

File support contains the DFT calculation data for this paper.
For a 4-atom unit cell with unit vector u1, u2 and u3,
the text files "support" contain the calculated DFT data for this paper
Alat[1][1], Alat[2][1] and Alat[3][1] give the unit vector u1 (Angstrom)
Alat[1][2], Alat[2][2] and Alat[3][2] give the unit vector u2 (Angstrom)
Alat[1][3], Alat[2][3] and Alat[3][3] give the unit vector u3 (Angstrom)
while the 10th to 15th columns give the stress components (GPa)
and the calculated energy (eV/atom) in column 16

Directory fig1 contains the files for fig1. File fig1a provides the energy data for Fig.1(a), calculated with the DFT  and approximated by the fifth-degree potential.
Columns 1 and 2 give \eta_1 and \eta_3, which are the data for x axis and y axis.
Columns 3 and 4 give the energy (eV/atom) calculated with the DFT  and approximated by the fifth-degree potential.
File fig1b contains the gradient of the energy (calculated both with the DFT and elastic potential) along x and y directions, i.e., along \eta_1 and \eta_3.
Columns 3 and 4 give the gradient of energy from DFT, while columns 5 and 6 give the gradient of energy from elastic approximation.

Directory fig2 contains the files for Fig.2.
File names contain the value of the lateral fixed stress (GPa, compression is positive),
for example, "0" for \sigma_22 = \sigma_33 = 0GPa and "-15" for \sigma_22 = \sigma_33 = -15 GPa.  Hydro means hydrostatic loading.
In each file, column 1 is \eta_3 followed by \sigma_33 (DFT) and \sigma_33 (Elastic approximation).

Directory fig3 contains the files for Fig.3.
File name interpretation is the same as in fig2 directory.
The first two columns give the straining path (\eta_1 and \eta_3) from DFT calculation followed by the straining path from elastic approximation.

Directory fig4 contains the files for Fig.4.
File "instability_DFT" contains the instability stresses from DFT calculation with first column labelled as \sigma_1, second \sigma_2 and third \sigma_3 (GPa).
File "instability_elastic" contains the instability stresses from elastic approximation.

Directory fig5 contains the files for Fig.5.
Files single_shear, double_shear and triple_shear contain the data for Fig.5(a).
Files "combination_shear_norm*" provide the data for Fig.5(b); each combination is specified by equation at the end of first line in each file.



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