- 1 JARVIS-FF
- 1.1 Crystal structures
- 1.2 Force-fields/interatomic potential
- 1.3 Elastic constant calculation
- 1.4 Vacancy formation
- 1.5 Surfaces
- 1.6 Phonon
- 2 JARVIS-DFT
- 2.1 Convergence
- 2.2 X-ray diffraction pattern
- 2.3 Electronic structure
- 2.4 Electrostatic potential
- 2.5 Optoelectronic properties with local/semilocal functional
- 2.6 Optoelectronic properties with MBJ functional
- 2.7 Elastic constants and finite-size phonons
- 2.8 Thermoelectric properties with constant time relaxation
- 3 JARVIS-ML

Details of the method can be found in our paper Evaluation and comparison of classical interatomic potentials through a user-friendly interactive web-interface

JARVIS-DFT was created to find new two-dimensional layered materials and create a consistemt database of functional materials. Complete database can be downloaded in JSON format now!

Calculations are done using VASP software. Convergence on KPOINTS and ENCUT is done with respect to total energy of the system within 0.001 eV tolerance. Please note convergence on KPOINTS and ENCUT is generally done for target properties, but here we assume energy-convergence with 0.001 eV should be sufficient for other properties also. The points on the curves are obtained with single-point calculation (nuber of ionic steps,NSW=1). However, for very accurate calculations, NSW>1 might be needed.After convergence, we optimize crystal structure with strict force and energy convergence criteria.

X-ray diffraction (XRD) pattern and the Radial distribution function (RDF) plots were obtained from the crystal structure using pymatgen. XRD peaks should be comparable to experiments mainly for bulk 3D materials. Relative intensities may differ.

Electronic structure is characterized using electronic density of states and bandstructure. DFT is generally predicted to underestimate bandgap of materials. Accurate band-gaps are obtained with higher level methods (with high computational requirement) such as HSE, GW, which are under progress. Total DOS, Orbital DOS and Element dos buttons are provided for density of states options at each webpage. Energy is rescaled to make Fermi-energy zero. In the bandstructure plot, spin up is is shown with blue lines while spin down are shown with red lines. Non-degenerate spin-up and spin-down states (if applicable) would imply a net orbital magnetic moment in the system.

The plane averaged electrostatic potential (ionic+Hartree) along x, y and z-directions at webpages. The red line shows the Fermi-energy while the green line shows the maximum value of the electrostatic potential. For slab structures (with vacuum along z-direction), the difference in these two values can be used to calculate work-function of the material.

Incident photon energy dependent dielectric function is calculated. Only interband optical transitions are taken into account.Please note the underestimatation of band-gap problem with DFT will reflect in the spectra as well. For very accurate optical properties GW/BSE calculation would be needed, which is yet to be done because of their very high computational cost. Optical properties for layered materials needs to be rescaled with the actual thickness to simulation z-box ratio.

Single point DFT calculation was carried out with meta-gga MBJ functional. This should give reasonable bandgap, and optical properties assuming the calculation was properly converged. Incident photon energy dependence of optical is shown at webpages. Only interband optical transitions are taken into account.

Elastic tensor was calculated for the conventional cell of the system with finite-difference method. For layered materials, the elastic constants are rescaled with respect to vacuum padding (see the input files) and the units for elastic coefficients are in N/m. Phonons obtained from this calcuation are also shown. WARNING: Please note this may not be the exact phonon modes of the system as we did not test the cell-size dependence of phonons yet. At least 1.2 nm x1.2 nm x1.2 nm or more is needed for obtaining reliable phonon spectrum. For systems having primitive-cell phonon representation tables, I denotes infrared activity and R denotes Raman active modes (where applicabale).

JARVIS-ML uses data from the atomistic calculations (mainly JARVIS-DFT) to predict properties of materials in a computationally cheap way for prescreeing of materials. JARVIS-ML uses structural as well as chemical features of materials.

More details coming soon !

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