Dear Amrish:
Let's sort things out:1. The energy shift is about constructing your basis 
functions. There is nothing you need to teston a huge supercell. Make the usual 
tests on small (minimal; single cell) systemsto be sure that your basis set 
construction permits you to obtain the reasonable description(of whatever your 
aims are: lattice parameters, bulk modulus, ...)2. The mesh cutoff, as it seems 
to me, a priori is not supposed to depend on the supercell size.Again, after 
you test it on prototype small systems, you can use the same valuefor large 
supercell.3 my workstation is not so powerful to deal with system like 500 
atoms... - then:why use such workstation? Or: why use 500 atoms? Or: why use 
Siesta?Best regardsAndrei

i am facing problem in my fdf file to take value of some parameters like mesh 
cutt off and energy shift parameters. my workstation is not so powerful to deal 
with system like 500 atoms so i don't want to waste time while test 
calculations on these parameters.can any one explain an alternate way to get 
approximate but the accurate value of mesh cutt off and energy shift for system 
consisting 500 atoms.
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warm regards
amrish sharmaresearch scholarDr. Isha Mudahar grouppunjabi university 
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