Dear Quantum Espresso Community, I am seeking advice on selecting appropriate van der Waals (vdW) functionals for calculating elastic properties of solids containing F, Cl, and Br. I'm particularly interested in the accuracy of PBEsol, PBEsol+D2, and PBEsol+D3. Concern: PBEsol+D2 and PBEsol+D3 sometimes yield significantly higher elastic constants (Cijkl) compared to PBEsol alone. In some cases, PBEsol+D2 values can be four to five times higher, raising concerns about vdW correction accuracy.
Question: Without experimental elastic constants & lattice parameters, how can I effectively choose the appropriate vdW correction (D2 or D3) for my calculations? Is there a recommended approach to identify the most suitable correction level for a specific system? Thank you for your time and assistance. Sincerely Sumantra Das, Graduate student Department of Metallurgical and Materials Engineering, Indian Institute of Technology Kharagpur
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