Understanding QEq Implementation in Lammps by Daniele Scopece
"Explore the QEq implementation in Lammps by Daniele Scopece, covering theory, algorithm, and critical questions on electrostatic potential and long-range interactions. Gain insights into the matrix calculations and factors contributing to the computational model."
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Presentation Transcript
Questions on QEq implemented in Lammps Daniele Scopece daniele.scopece.science@gmail.com 2014-09-15 started 1
What is this presentation about ? Here I shortly resume my understanding of the QEq implementation in Lammps. In addition I write my questions on what I do not understand, so to be hopefully helpful to others. I refer to the case qeq/slater since I am interested in that. 2
Quick Resume of Theory 3
Theory of the Algorithm ( ) = (Expression in zei zej) 5
Question 01 Inclusive of both short and long-ranged H in lammps = Vij here The complete H from theory would be The short-ranged terms of the matrix H is computed in the subroutine calculate_H: Why is this factor here ? It is not present in the equation 9
Question 02 These seem just the short-ranged terms of the electrostatic potential. Where are the long-ranged terms (in reciprocal space?) computed ? I couldn t find them ( ) = (Expression in zei zej) 10
Question 03 In the function sparse_matvec, the matrix H is multiplied by x and the result stored in q. The final expression is: self part of the long-range interactions Factor of Question-01 (This comes from the variable woself) Where does this term come from ? Why does the erfc appears twice in this expression ? Where is the long-ranged (reciprocal space) term here ? 11
Question 04 In the file fix_qeq_slater.cpp is also a function called calculate_H_wolf But in the examples online this is not invoked. What is that for ? In what case is it invoked ? 12
Thank you for your help 13
