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Vacuum level Date: 2014/04/04 23:35 Name: Alfonso Sanchez   <alfonso.sanchez@tyndall.ie> Hi all, I want to calculate the vacuum level on some slab calculations but don't know how to. I'd really appreciate it if someone would answer these two questions: 1 ) On this topic ( http://www.openmx-square.org/forum/patio.cgi?mode=view&no=1586 ) T. Ozaki mentions: "> 3. if I wanna see the vaccum level, is vhart.cube the right file? Yes it is. By using the vhart.cube file, one can calculate the work function. However, one has to allocate basis functions in the vacuum region using empty atoms, where just adding one layer consisting of basis functions from the top most layer is enough to reproduce the corresponding plane-wave result. " But I'm not sure what "adding one layer of basis functions from the top most layer" means. Is it that that this layer must be added directly on top of the slab and vhart will be "zero" (vacuum) there? or add the empty orbitals there and "measure" the vacuum level at the centre of the vacuum separating the slab from its periodic images? I'm confused by the whole thing really. 2 ) Once the previous question is resolved... Does anyone know of a good way of reading the potential in the cube file? I know XCrysDen can read the file, but it shows the actual structure rather than the potential. Thanks in advance for your time, Alfonso

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Re: Vacuum level ( No.1 ) Date: 2014/04/05 02:21 Name: Alfonso Sanchez  <alfonso.sanchez@tyndall.ie> Regarding question 2) : I've managed to read the data with VESTA. Is there any way to relate the value for the chemical potential printed in *.out to the 0 of energy in band structure plots? (as generated with bandgnu13) Re: Vacuum level ( No.2 ) Date: 2014/04/16 06:44 Name: T. Ozaki Hi, > But I'm not sure what "adding one layer of basis functions from the top most layer" > means. Is it that that this layer must be added directly on top of the slab and > vhart will be "zero" (vacuum) there? or add the empty orbitals there and "measure" > the vacuum level at > the centre of the vacuum separating the slab from its periodic images? I'm confused by > the whole thing really. Imagine you have infinite bulk along z-direction illustrated by .... o0 o1 o2 o3 o4 o5 o6 o7 o8 o9 o10 o11 o12 o13 ....... where o means an atom, and .... means the infinity. Then, you cut the bulk to create the surface as o5 o6 o7 o8 o9 This is a slab model. Now we add the empty atoms as x4 o5 o6 o7 o8 o9 x10 where x means the empty atom, and the positions of x4 and x10 are the same as o4 and o10, respectively. This illustration is for a simple clean surface with no surface reconstruction. For general cases, we can determine the position of empty atoms by assuming the clean surface with no surface reconstruction. Fortunately, a subtle difference in the choice of position does not change largely the calculated value of work function. We have tested the scheme to calculate work functions of a wide variety of metallic surfaces, and obtained results well compared to plane wave calculations. > Is there any way to relate the value for the chemical potential printed in *.out to > the 0 of energy in band structure plots? (as generated with bandgnu13) The 0 of energy in band structure is nothing but the chemical potential in *.out. Best regards, TO Re: Vacuum level ( No.3 ) Date: 2014/04/16 06:28 Name: Alfonso Sanchez  <alfonso.sanchez@tyndall.ie> Thank you Prof. Ozaki, that was very clear.

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