Hi, On Fri, 1 Jul 2022, 22:00 肖威, <xiaowei951...@163.com> wrote:

> Dear SIESTA developers and users, > > I recently read Papior et al. 's article on Phys. Chem. Chem. Phys. > entitled "Manipulating the voltage drop in graphene nanojunctions using a > gate potential (DOI: 10.1039/C5CP04613K)". I am very interested in the > method of adding gate voltage to a system in this article and try to learn > how to use it. However, I have encountered some difficulties in the > process, and I'm really looking forward to some help. > > 1. When I use the square (Bounded plane) option in Gate, I need to set > the starting point of the square and two spanning vectors. As shown below > (copied from the SIESTA 4.1-b4 manual). > > %block Geometry.Hartree > > square 1. eV # The lifting potential on the geometry > > gauss 1. 2. Ang # the std. and the cut-off length > > 1.0 1.0 1.0 Ang # The starting point of the square > > 2.0 0.5 0.2 Ang # The first spanning vector > > 0.0 2.5 0.2 Ang # The second spanning vector > > %endblock Geometry.Hartree > > But we all know that two points define a vector, so do the coordinates > that define the spanning vector in the example above represent the end > point of the vector? If so, what is the starting point of this spanning > vector? Is the spanning vector starting at the origin (0 0 0) or at the > starting point of the square (1.0 1.0 1.0) defined in the example above? > > I have the same question about plane (Infinite plane, a vector) and Box > (three vectors) in Gate. > There are 3 points, (1,2,3) the vectors go from 1-2 and 1-3. In the square geometry the vectors form a bounded surface, in the infinite plane the length of them doesn't matter as they will be considered infinite. > 2. Whether a shorter vacuum layer in the direction of adding Gate makes > self-consistency difficult to converge. How to determine the appropriate > length of vacuum layer? > The most simple thing is (if you don't have periodicity along the field generated by the gate) to add a slab dipole correction, and add vacuum corresponding to 1.5 times the distance between your structure and the gate. Note however that the hartree gate merely changes the electrostatic potential in the defined region, i.e. it is not a boundary condition in the generic sense. > I'm really looking forward to some help. > > Thank you very much! > > Wei > > 肖威 > xiaowei951...@163.com > > <https://maas.mail.163.com/dashi-web-extend/html/proSignature.html?ftlId=1&name=%E8%82%96%E5%A8%81&uid=xiaowei951020%40163.com&iconUrl=https%3A%2F%2Fmail-online.nosdn.127.net%2Fqiyelogo%2FdefaultAvatar.png&items=%5B%22xiaowei951020%40163.com%22%5D> > > -- > SIESTA is supported by the Spanish Research Agency (AEI) and by the > European H2020 MaX Centre of Excellence (http://www.max-centre.eu/) >

-- SIESTA is supported by the Spanish Research Agency (AEI) and by the European H2020 MaX Centre of Excellence (http://www.max-centre.eu/)