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exercises:2015_ethz_mmm:basis_sets [2015/02/06 17:49] – external edit 127.0.0.1exercises:2015_ethz_mmm:basis_sets [2020/08/21 10:15] (current) – external edit 127.0.0.1
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 ====== Basis Sets ====== ====== Basis Sets ======
-In this exericse you will compare different basis sets and use them for computing the binding energy of an H2 molecule.+In this exercise you will compare different basis sets and use them for computing the binding energy of an H$_2$ molecule.
  
 The cp2k basis set format is described in detail [[:basis_sets|here]]. The cp2k basis set format is described in detail [[:basis_sets|here]].
  
-===== Part I: Different basis sets for H and H2 =====+===== Part I: Different basis sets for H and H$_2$ =====
 ==== 1.Step ==== ==== 1.Step ====
  
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 <code - mybasis.inp >  <code - mybasis.inp > 
- 
 &GLOBAL &GLOBAL
   PROJECT H-mybasis   PROJECT H-mybasis
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       METHOD GAPW                          ! Method: gaussian and augmented plane waves        METHOD GAPW                          ! Method: gaussian and augmented plane waves 
     &END QS     &END QS
-    &XC                                    ! Parametes needed to compute the electronic exchange potential +    &XC                                    ! Parameters needed to compute the electronic exchange potential 
       &XC_FUNCTIONAL NONE                  ! No xc_functional       &XC_FUNCTIONAL NONE                  ! No xc_functional
       &END XC_FUNCTIONAL       &END XC_FUNCTIONAL
       &HF                                  ! Hartree Fock exchange. In this case is 100% (no fraction specified).                           &HF                                  ! Hartree Fock exchange. In this case is 100% (no fraction specified).                    
-        &SCREENING                         ! Screening of the electronic repulstion up to the given threshold. This section is needed+        &SCREENING                         ! Screening of the electronic repulsion up to the given threshold. This section is needed
           EPS_SCHWARZ 1.0E-10              ! Threshold specification           EPS_SCHWARZ 1.0E-10              ! Threshold specification
         &END SCREENING         &END SCREENING
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     &CELL     &CELL
       ABC 10.0 10.0 10.0       ABC 10.0 10.0 10.0
-      PERIODIC NONE                        ! Non periodic calculations. That's why the POISSON scetion is needed +      PERIODIC NONE                        ! Non periodic calculations. That's why the POISSON section is needed 
     &END CELL     &END CELL
     &COORD     &COORD
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      0.6 1      0.6 1
      &END      &END
-     POTENTIAL ALL                         ! Specifes that the potential is for all electron calculations.+     POTENTIAL ALL                         ! Species that the potential is for all electron calculations.
      &POTENTIAL                            ! Usual all electron potential for H       &POTENTIAL                            ! Usual all electron potential for H 
      1    0    0      1    0    0
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-^ Basis set                     ^ Energy  H (Eh)       ^ +^ Basis set                     ^ Energy  H ($E_h$)      ^       
-| mybasis (from given input)    | .... | +| mybasis (from given input)    | ....                   | 
-| basis try 1                   | .... |  +| basis try 1                   | ....                   |  
-| basis try 2                   | .... | +| basis try 2                   | ....                   | 
-| ....                          | .... | +| ....                          | ....                   | 
-| pc-0                          | .... |  +| pc-0                          | ....                   |  
-| pc-1                          | .... | +| pc-1                          | ....                   | 
-| pc-2                          | .... | +| pc-2                          | ....                   | 
  
 <note tip>Is always good to keep record of self-created basis sets, to track the effect of a change in value and number of exponents, contractions....etc.. </note> <note tip>Is always good to keep record of self-created basis sets, to track the effect of a change in value and number of exponents, contractions....etc.. </note>
  
-Repeat the procedure for H2. \\ +==== 3.Step ==== 
-H2 coordinates:  +Repeat the procedure for H$_2$. For this you will have to add a second H atom to the coordinate section and run a **geometry optimization** to determine the equilibrium distance. Howto run a geometry optimization was covered in a [[geometry_optimization|previous exercise]]. Note that the equilibrium distance will depend on your basis set.
-<code> +
-H 0 0 0      +
-H 0.75 0 0    +
-</code>+
  
-<note important> The H2 molecule does not have unpaired electrons. Remember to take out the LSD and MULTIPLICITY keywords. </note>+<note important> The H$_2$ molecule does not have unpaired electrons. Remember to take out the LSD and MULTIPLICITY keywords.</note>
  
-===== Part II: Estimate the binding energy of H2 =====+===== Part II: Estimate the binding energy of H$_2$ =====
  
-Binding energy: \\ +Based on the formula for the //binding energy//, you can now update your table.
  
-\[ \sum E_\text{products} -  \sum E_\text{rectants} = E(H_2) - 2 \cdot E(H) \]+\[ \sum E_\text{products} -  \sum E_\text{reactants} = E(H_2) - 2 \cdot E(H) \]
  
-<note important> The binding energy value is significant only if the same basis is used for both reactants and products. </note> 
  
 +^ Basis set                  ^ Energy H [$E_h$] ^ Energy H$_2$ [$E_h$] ^ Distance H$_2$ [$Å$] ^ Binding Energy H$_2$ [$E_h$] ^
 +| mybasis (from given input) | ....             | ....              | ....            | ....                      |
 +| basis try 1                | ....             | ....              | ....            | ....                      |
 +| basis try 2                | ....             | ....              | ....            | ....                      |
 +| ....                       | ....             | ....              | ....            | ....                      |
 +| pc-0                       | ....             | ....              | ....            | ....                      |
 +| pc-1                       | ....             | ....              | ....            | ....                      |
 +| pc-2                       | ....             | ....              | ....            | ....                      |
 +| ....                       | ....             | ....              | ....            | ....                      |
  
-You can now update your table: +<note important>The binding energy is only significant if all terms were calculated with the same basis-set.</note>
- +
-^ Basis set                     ^ Energy  H (Eh)       ^ Energy H2 (Eh) ^ Binding Energy H2 (Eh) ^ +
-| mybasis (from given input)    | .... | .... | ....  | +
-| basis try 1                   | .... | .... | ....  | +
-| basis try 2                   | .... | .... | ....  | +
-| ....                          | .... | .... | ....  | +
-| pc-0                          | .... | .... | ....  | +
-| pc-1                          | .... | .... | ....  | +
-| pc-2                          | .... | .... | ....  | +
-| ....                          | .... | .... | ....  |+
  
 ===== Part III: Questions ===== ===== Part III: Questions =====
- +  - What is the effect of changing the exponents in a basis set? 
-- What is the effect of:\\ +  - What is the effect of adding p- and d-function to the basis set? Do H and H$_2$ respond differently?
-  * increasing/decreasing the value of the exponents for the given basis? +
-  * adding sets with p,d symmetry to the basis? You have the same effect in H and H2? +
- +
- +
-===== Part IV: Additional basis sets =====+
  
  
 +===== Appendix: Literature Basis Sets =====
  
 +<code>
 H  pc-0 H  pc-0
   2   2
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           1.25000000          1.00000000           1.25000000          1.00000000
  
- +</code>
  
  
exercises/2015_ethz_mmm/basis_sets.1423244958.txt.gz · Last modified: 2020/08/21 10:14 (external edit)