[QE-users] ESM calculation with tot_charge in QE

[Giuseppe Mattioli]

Dear Minoru
I've read the PRB paper you suggested and I would be very interested  
in testing such a new 3D-RISM extension of the ESM method of yours.  
The paper mention a QE implementation, but I've not seen any  
documentation in QE 6.2.1 yet. Shall I find it either in the unstable  
version or in a next stable release?
Thank you in advance
Giuseppe

Quoting 大谷?g <minoru.otani at aist.go.jp>:

> Dear Hong,
>
> In the boundary condition bc1, i.e. the open boundary condition, we  
> need to prepare a neutral system. Because there are divergent terms  
> in the total energy and the electrostatic potential. If your system  
> is neutral, i.e. tot_charge=0, you can get an appropriate result  
> with ESM, but your system is charged, i.e. tot_charge!=0, you can  
> not get a physically meaningful result.
>
> In other boundary conditions such as bc2 and bc3, the ESM  
> automatically introduce compensation charge. Thus the whole system  
> is neutral. In other words, there are no divergent terms in the  
> total energy and the electrostatic potential for bc2 and bc3.
>
> As you can understand from above description, the problem is the  
> divergent term. If you can ensure that the additional charge induced  
> in the system with bc1 will completely be screened by another  
> medium, you can use the bc1 boundary condition. In this case, the  
> total energy and the electrostatic potential are physically  
> meaningful values. In other words, the divergent term from another  
> medium eliminates that from the system.
>
> If you want to dig into the details of this, you can read the  
> following paper: Phys Rev. B 96, 115429 (2017).
>
> In short, you can not use bc1 with a charged system.
>
> Best regard,
> Minoru
>
> --------------------------------------------------------------------------------------------------------
> National Institute of Advanced Industrial Science and Technology,
> Research Centre for Computational Design of Advanced Functional Materials
> E-mail: minoru.otani at aist.go.jp
> --------------------------------------------------------------------------------------------------------
>
>
> ________________________________________
> From: users <users-bounces at lists.quantum-espresso.org> on behalf of  
> Honghui Wu <hhwuaa at connect.ust.hk>
> Sent: Saturday, March 10, 2018 2:38:38 AM
> To: users at lists.quantum-espresso.org
> Subject: [QE-users] ESM calculation with tot_charge in QE
>
> Dear all,
>
> Can we use the charged system (tot_charge= a finite value) with the
> vacuum-slab-vacuum boundary condition (esm_bc = 'bc1') in Quantum ESPRESSO?
>
> In the OpenMX website, I find the ESM developer writes 'ESM.switch =
> on1: Both ESM (I) and (II) are semi-infinite vacuum media. In this case,
> note that the total charge of a calculation system should be neutral.
> The keyword 'scf.system.charge' should be set to be zero.'.
> However, I did not find the similar description of the esm_bc= 'bc1' :
> Vacuum-slab-vacuum (open boundary conditions).  Does it mean we can use
> the charged system (tot_charge= a finite value) with the
> vacuum-slab-vacuum boundary condition in Quantum ESPRESSO?
>
> Thank you!
>
> Best regards,
> Hong
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GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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E-mail: <giuseppe.mattioli at ism.cnr.it>