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exercises:2017_uzh_cmest:pdos [2017/10/17 15:48] – jglanexercises:2017_uzh_cmest:pdos [2020/08/21 10:15] (current) – external edit 127.0.0.1
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-======= Projected density of states for graphene and h-BN =======+======= Projected density of states and Band structure for WO$_3$ =======
  
-In the following exercise we are going to look at the density of states of WO$_3$:+In this exercise, you will carry out Density Of States(DOS) and band structure calculation using K-point sampling for Cubic lattice WO$_3$. The reference DOS and band structure you can find in [[http://pubs.acs.org/doi/abs/10.1021/cm3032225|this paper]] 
 + 
 +{{:exercises:2017_uzh_cmest:wo3.jpeg?1200|}} 
 + 
 +====== Getting the PDOS ====== 
 + 
 +In the following exercise we are going to look at the density of states of <chem>WO3</chem>:
  
 Similar to the previous exercise we write the coordinates in term of the unit cell: Similar to the previous exercise we write the coordinates in term of the unit cell:
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  <code>python get-smearing-pdos.py file.pdos</code>  <code>python get-smearing-pdos.py file.pdos</code>
  
-Alternatively, you could also use the [[https://raw.githubusercontent.com/dev-zero/cp2k-tools/master/scripts/cp2k_pdos.py|Python script]] developed by Tiziano.+Alternatively, you could also use the [[https://raw.githubusercontent.com/dev-zero/cp2k-tools/master/scripts/cp2k_pdos.py|Python script]] developed by Tiziano, the parser bug was fixed already.
  
 <note important>Different $\sigma$ values give you different convolution, which mean the lineshape is different. A reasonable $\sigma$ value is required to get a good PDOS plot. When visualize the PDOS, only energy region close to the Fermi level is interesting. One need to adapt the xrange properly.</note> <note important>Different $\sigma$ values give you different convolution, which mean the lineshape is different. A reasonable $\sigma$ value is required to get a good PDOS plot. When visualize the PDOS, only energy region close to the Fermi level is interesting. One need to adapt the xrange properly.</note>
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 While some of the new options to help with convergence are of numerical nature, [[howto:static_calculation#adding_smearing|the smearing is not]]. While some of the new options to help with convergence are of numerical nature, [[howto:static_calculation#adding_smearing|the smearing is not]].
  
 +
 +<note>
   * Repeat the above calculation for the different multiple cells 3x3x3, 4x4x4   * Repeat the above calculation for the different multiple cells 3x3x3, 4x4x4
-  * Do you see why it is necessary to do the unit cell replication? Hints: does WO$_3$ have a band gap? Compare the plots for 3x3x3 and 4x4x4.+  * Get the Total DOS and PDOS of O$_2p$ and W$_5d$ orbitals and compare to the literature value. 
 +  * Do you see why it is necessary to do the unit cell replication?   
 +  * What is the value of WO$_3$ band gap? Compare the plots for 3x3x3 and 4x4x4.
   * .. which state ($s$, $p_x$, ..) is mainly responsible for that?   * .. which state ($s$, $p_x$, ..) is mainly responsible for that?
 +  * Change the $\sigma$ value in convolution program, and determine a reasonable value for the PDOS plot
 +</note>
  
 +====== Getting the band structure of WO$_3$ Lattice ======
  
-======= Getting the band structure of WO$_3$ Lattice ======= +To get the band structure for <chem>WO3</chem>, only a few changes are required compared to the previous example for [[PDOS|calculating the PDOS]]: 
- + 
-In this exercise, you will carry out band structure calculation using K-point sampling for Cubic lattice WO$_3$. The reference band structure you can find in [[http://pubs.acs.org/doi/abs/10.1021/cm3032225|this paper]] +
- +
-{{:exercises:2017_uzh_cmest:wo3.jpeg?1200|}} +
- +
-To get the band structure for WO3, only a few changes are required compared to the previous example for [[PDOS|calculating the PDOS]]: +
 <code - WO3-bs.inp> <code - WO3-bs.inp>
 &GLOBAL &GLOBAL
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       &KPOINTS       &KPOINTS
          SCHEME MONKHORST-PACK 3 3 1          SCHEME MONKHORST-PACK 3 3 1
-         SYMMETRY OFF 
          WAVEFUNCTIONS REAL          WAVEFUNCTIONS REAL
-         FULL_GRID .TRUE. +         SYMMETRY .FALSE. 
-         PARALLEL_GROUP_SIZE  0+         FULL_GRID .FALSE. 
 +         PARALLEL_GROUP_SIZE -1
       &END KPOINTS       &END KPOINTS
       &PRINT       &PRINT
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   * The keyword ''NPOINTS'' specifies how many points (in the addition to the starting point) should be sampled between two special points.   * The keyword ''NPOINTS'' specifies how many points (in the addition to the starting point) should be sampled between two special points.
   * The ''SPECIAL_POINT'' keyword is used to specify the start-, mid- and endpoints of the line. Those points usually denote special points in the reciprocal lattice/unit cell, like the $\Gamma$, $M$ or $K$ point. You can find the definition for these in the appendix section of [[http://www.sciencedirect.com/science/article/pii/S0927025610002697|this paper]]. This keyword can also be specified multiple times, making it possible to directly get the band structure for a complete //path//.   * The ''SPECIAL_POINT'' keyword is used to specify the start-, mid- and endpoints of the line. Those points usually denote special points in the reciprocal lattice/unit cell, like the $\Gamma$, $M$ or $K$ point. You can find the definition for these in the appendix section of [[http://www.sciencedirect.com/science/article/pii/S0927025610002697|this paper]]. This keyword can also be specified multiple times, making it possible to directly get the band structure for a complete //path//.
 +
 +<note tip>You are encouraged to use [[ http://tools.materialscloud.org/seekpath|SeeK-path Tool]] when doing the sampling via K-Points to get a skeleton input file for CP2K with the important paths in the reciprocal space. Give SeeK-path the following as your XYZ file and specify a simple cubic cell with the lattice constant $a$ as specified below as well:
 +<code - WO3-cubic.xyz>
 +4
 +WO3; a=3.810000
 + W    0.000000    0.000000    0.000000
 + O    1.905000    0.000000    0.000000
 + O    0.000000    1.905000    0.000000
 + O    0.000000    0.000000    1.905000
 +</code>
 +</note>
 +
  
 Now, when you run this input file you will get in addition the the output file, a file named ''WO3.bs'' which will look similar to the following: Now, when you run this input file you will get in addition the the output file, a file named ''WO3.bs'' which will look similar to the following:
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 For each set there is a block named ''SET'' with the special points listed as ''POINT'', followed by sub-blocks for each K-Point containing the energies for each MO. For each set there is a block named ''SET'' with the special points listed as ''POINT'', followed by sub-blocks for each K-Point containing the energies for each MO.
  
 +<note>
 Your tasks: Your tasks:
  
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   * Compare your plot with plots from literature. What is different?   * Compare your plot with plots from literature. What is different?
   * How many orbital energies do you get and why? Try to change the input to get more unoccupied orbitals.   * How many orbital energies do you get and why? Try to change the input to get more unoccupied orbitals.
 +</note>
 +
  
 To convert the band structure file to a file which can be plotted directly, you can use the script ''cp2k_bs2csv.py'' from below, which when passed a band structure file ''WO3.bs'' as an argument will write files ''WO3.bs-set-1.csv'' for each set containing the K-Point coordinates and the energies in one line. To convert the band structure file to a file which can be plotted directly, you can use the script ''cp2k_bs2csv.py'' from below, which when passed a band structure file ''WO3.bs'' as an argument will write files ''WO3.bs-set-1.csv'' for each set containing the K-Point coordinates and the energies in one line.
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 </file> </file>
- 
exercises/2017_uzh_cmest/pdos.1508255329.txt.gz · Last modified: 2020/08/21 10:15 (external edit)