Dear Prasenjit Ghosh, Please refer to Figure 1 in the original ESM paper (PRB 73, 115407 (2006)). The position of the right edge of the unit cell is z_0, while the position of the ESM region is z_1. Thus, the definition of esm_w is as follows: esm_w=z_1−z_0
Typically, we try to keep the unit cell size (z_0) as small as possible. However, the position of the ESM region depends on the model you want to simulate. For example, if you are modeling a parallel plate capacitor with ESM, the position of z_1 is determined by the thickness of the vacuum region between the electrodes. Please remember that z_1 must be greater than or equal to z_0, so esm_w is either positive or zero. Best regards, Minoru > On Apr 23, 2024, at 19:16, Ghosh, Prasenjit <[email protected]> wrote: > > Dear all, > > I am trying to perform calculations for a charged system with assume_isolated > = "esm" and using a vacuum/metal boundary condition (esm_bc='bc3'). > However, I am confused regarding how to choose the position offset for the > start of the effective screening region (esm_w). > Some preliminary calculations by varying esm_w suggests that the results (for > eg. the electrostatic potential on the vacuum side, magnitude of the bias > applied to the surface, etc.) > strongly depends on the choice of the "esm_w" variable. > > Can anyone please suggest how to choose an optimal value of "esm_w"? > > Thanking you in advance. > > With regards, > > Prasenjit Ghosh > IISER Pune > _______________________________________________ > The Quantum ESPRESSO community stands by the Ukrainian > people and expresses its concerns about the devastating > effects that the Russian military offensive has on their > country and on the free and peaceful scientific, cultural, > and economic cooperation amongst peoples > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users _______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
