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exercises:2017_uzh_cmest:defects_in_silicon [2017/10/31 18:19] tmuellerexercises:2017_uzh_cmest:defects_in_silicon [2020/08/21 10:15] (current) – external edit 127.0.0.1
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 </code> </code>
  
-Create a second input file ''silicon64.inp'' based on the above with 64 atoms in the cell (do not use ''MULTIPLE_UNIT_CELL'' but actually replicate the ''Si ...'' entries by hand (and make sure you don't forget to update the ''CELL'').+Create a second input file ''silicon64.inp'' based on the above with 64 atoms in the cell (do not use ''MULTIPLE_UNIT_CELL'' but actually replicate the ''Si ...'' entries by hand and make sure you don't forget to update the ''CELL'').
  
 Run the calculation for both geometries and compare the single atom energy for both of them to make sure you got it right. Run the calculation for both geometries and compare the single atom energy for both of them to make sure you got it right.
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 </note> </note>
  
-For both geometries create a vacancy by removing one Silicon, re-calculate the total energy and compare it to the total energy of the intact bulk Silicon minus the single atom energy. What do you observe? Why?+For both geometries create a vacancy by removing one Silicon atom, re-calculate the total energy and compare it to the total energy of the intact bulk Silicon minus the single atom energy. What do you observe? Why?
  
 <note tip>You may have to employ some of the techniques mentioned in [[PDOS|Projected density of states and Band structure for WO$_3$]] to make the calculations converge.</note> <note tip>You may have to employ some of the techniques mentioned in [[PDOS|Projected density of states and Band structure for WO$_3$]] to make the calculations converge.</note>
  
-Finally, calculate the band structure for the silicon8 geometries (with and without vacancy) as shown in the exercise [[PDOS|Projected density of states and Band structure for WO$_3$]] between $\Gamma$, $X$, $K$, $\Gamma$ and compare them.+====== Observing changes in the density of states ======
  
-<note tip>You can use [[http://tools.materialscloud.org/seekpath/|SeeK-Path]] with the following XYZ file again to obtain a CP2K input file skeleton with the required path:+Finally we are going to look at the change of the density of states due to the vacancy:
  
-<code xyz silicon.xyz> +Alter the input files for the small geometry (the ''silicon8'') with and without the vacancy to print out the projected density of states as shown in [[PDOS|a previous exercise]] and plot the total density of states for both casesWhat do you observe when comparing the band gap of the two geometries? 
-8 + 
-Bulk Silicon +Now do a geometry optimization on the ''silicon8'' structure with the vacancy and plot the total density of states on that relaxed structure againCompare again to the total density of states for the unaltered structure, what do you see?
-Si    0              0              0 +
-Si    0              2.7153487500   2.7153487500 +
-Si    2.7153487500   2.7153487500   0 +
-Si    2.7153487500                2.7153487500 +
-Si    4.07302312500  1.35767437500  4.07302312500 +
-Si    1.35767437500  1.35767437500  1.35767437500 +
-Si    1.35767437500  4.07302312500  4.07302312500 +
-Si    4.07302312500  4.07302312500  1.35767437500 +
-</code> +
-</note>+
exercises/2017_uzh_cmest/defects_in_silicon.1509473968.txt.gz · Last modified: 2020/08/21 10:15 (external edit)