[Pw_forum] ESM method

大谷実 minoru.otani at aist.go.jp
Wed Jul 26 14:48:57 CEST 2017

Dear Rajesh,

Yes, AA is angstrom. Currently you can not use vc-relax. You can do a geometry optimization with fixed cell so you can use “relax". Regarding the positive total energy, first, you should try the ESM_example calculations and compare the results with the reference results. Did you get reasonable results? If yes, I can not understand the origin of your problem now.

Best regards,
Minoru Otani
National Institute of Advanced Industrial Science and Technology
Research Centre for Computational Design of Advanced Functional Materials
email : minoru.otani at aist.go.jp<mailto:minoru.otani at aist.go.jp>

On Jul 26, 2017, at 21:14, Rajesh <creativeidleminds at gmail.com> wrote:

Dear Minoru,
Thanks for quick response. Here AA=angstrom?? I tried esm method in vc-relax calculations with two boundary conditions
1. pbc and 2. bc1.

For pbc conditions the energy comes out too be negative but for bc1 it was positive ( with no esm_w value). Energy of solids is always negative. So where I am wrong?



On Wed, Jul 26, 2017 at 5:32 PM, 大谷実 <minoru.otani at aist.go.jp<mailto:minoru.otani at aist.go.jp>> wrote:
Dear Rajesh,

I can not fully understand your configuration. But let me suppose you have a single graphene
sheet in a calculation cell with 15AA vacuum on both sides.

L_z = 15AA + graphene sheet (0 AA) + 15AA = 30 AA
The graphene sheet is located at z=0.

For bc1 calculation, you do not need to use esm_w. For bc2 or bc3, if you want to put ESM(metal) electrode at the position of z= +/- 15AA (for bc2) or z= +15AA (for bc3), esm_w = 0.0. The esm_w specifies the offset value of the ESM(metal) electrode position from the cell edge (z=+/- L_z/2). Thus, if you want to put the electrode on z= + 18AA, the esm_w must be 3AA.

Best regards,
From: pw_forum-bounces at pwscf.org<mailto:pw_forum-bounces at pwscf.org> <pw_forum-bounces at pwscf.org<mailto:pw_forum-bounces at pwscf.org>> on behalf of Rajesh <creativeidleminds at gmail.com<mailto:creativeidleminds at gmail.com>>
Sent: Wednesday, July 26, 2017 8:34:20 PM
To: PWSCF Forum
Subject: [Pw_forum] ESM method

Dear Users,

in the manual I find this "ESM region begins at z = +/- [L_z/2 + esm_w]". Suppose I have graphene sheet of with 3.33Angstrom as its thickness and I want to apply a 15Angstrom vacuum on both sides of the sheet. What are z and L_z/2 here?? is L_z/2=3.33A?? and Then what will be the value of position offset esm_w?? is esm_w=15angstrom?? and z=3.33+15+15=33.3 Angstrom? Please explain.

Thank you.


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