[QE-users] Optimal Smearing Energy for Electronic Structure Calculations

[David Yao ANSI]

Dear QE users, 





I am David Ansi, a master's student from the University of Science and Technology (Ghana), currently engaged in electronic structure calculations. My current focus is on calculating the band structure and density of states (DOS) of molybdenum-doped graphene. However, during my SCF calculation, I encountered a recurring message for several iteration steps: 



"Minimization algorithm failed to find Fermi energy: reverting to bisection. Possible cause: smearing is larger than the electronic band-gap." 



I was using the Marzari-Vanderbilt smearing method with a degauss value of 0.01. Also, the resulting DOS plot displays negative density of states, which is inconsistent with physical reality. 

In an attempt to better understand the impact of smearing energy, I followed the guidelines presented in "Quantum ESPRESSO Course for Solid-State Physics" by Ahmad R. T. I plotted the total energy as a function of smearing energy using various smearing functions. Unfortunately, I am unsure about how to determine the optimal smearing energy and its implications for accuracy and stability. I would greatly appreciate assistance in making informed decisions regarding the choice of smearing energy. 

Regards, 
David Ansi 

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