1. Calculation of DFT Energy for Silicon bulk
To use the previous setting which achieved convergence, set the scripting option to General, and set the input parameters. In the previous examples, Weekly tip #1 and Weekly tip #2, we had obtained the proper input parameter set of single crystal silicon: cutoff energy of 40–240 Ry, and 6x6x6 k-points grid.
Set the job name and click the 'Start Job!' button to start the calculation.
It takes about several tens seconds or minutes to make an SCF calculation for the structures having a good symmetry structure such as silicon single crystal.
The progress of the submitted job is displayed in the dashboard of the menu bar on the upper section.
Once the calculation is complete, come back to the Quantum Espresso module and click the 'Update' button or refresh the page to check whether the end message is normally displayed.
Once the green finish message is displayed, the calculation job is has been finished normally.
Add the energy module and connect to the Quantum Espresso module to check the final energy value. The silicon conventional cell, the calculation model, is consisted of 8 atoms. Therefore, this energy is for eight atoms.
2. Calculation of DFT Energy for Silicon Single Atom
Next, we need to perform DFT calculation for a single atom to calculate the cohesive energy. As like bulk calculation, you should prepare the structure to calculate for the single atom.
You can add a new structure builder, but another structure can be added by opening the Structure List ( button) on the upper right of the visualizer of the existing structure builder. Click the green + button to add a new structure, and create a cell with only one atom in the crystal builder menu.
Click the 'CRYSTAL' icon to select the crystal builder menu. Make the single atom cell with referring the following inputs.
For cutoff energy, 40–240 Ry, which was used in the bulk calculation and be decided for a convergence setting in the Weekly tip #1, needs to be used.
However, as the single atom DFT energy is not related to k-points for the fully converged case, gamma (1x1x1 grid, the one k-point) can be set for a fast calculation.
Once the calculation is complete, click the 'Update' button or refresh the page, and check if the calculation is normally finished. If so, add an energy module to check the energy.
3. Calculation of Cohesive Energy
In the memo module, you can use the cell reference and basic arithmetic operations, by writing directly the cell address. Add a memo module, and paste the final energy value of the silicon bulk and the atom to compare the data easily.
Calculate the energy for each atom, and find the difference to get the Ecoh/atom of the silicon.
5. Cohesive Energy for Heusler Alloy
Heusler alloy is having chemical formula of X2YZ. In this time, the cohesive energy can be calculated by the following equation.
 Parrill A. L., Lipkowitz, K. B. (Eds.). (2016). Reviews in Computational Chemistry, Volume 29. 44-47, Wiley
 Khandy, S. A., Islam, I., Gupta, D. C., Khenata, R., & Laref, A. (2019). Lattice dynamics, mechanical stability and electronic structure of Fe-based Heusler semiconductors. Scientific reports, 9(1), 1-8.
 Yin, M. T., & Cohen, M. L. (1982). Theory of static structural properties, crystal stability, and phase transformations: Application to Si and Ge. Physical Review B, 26(10), 5668–5687. doi:10.1103/physrevb.26.5668