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exercise:basis_sets [2014/03/25 14:56] – scleliaexercise:basis_sets [2014/04/02 15:22] – [Basis Sets] oschuett
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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 exericse you will compare different basis sets and use them for computing the binding energy of an H2 molecule.
  
-The cp2k basis set format is the following: +The cp2k basis set format is described in detail [[:basis_sets|here]].
- +
-<code> +
- +
-Nsets +
-  n1 lmin lmax Nexp Ncontr +
-    exp1 contr1 contr2 contr3 ... +
-    exp2 contr4 contr5 contr6 ... +
-    Nexp.... +
-  n2 lmin lmax Nexp Ncontr +
-    exp1 contr1 contr2 contr3 ... +
-    exp2 contr4 contr5 contr6 ... +
-    Nexp.... +
-    ... +
-</code> +
-\\ +
-Nsets = number of sets.  \\  +
-n1,n2... = main quantum number (but it gets ignored by the program!) \\ +
-lmin = min //l// (angular quantum number) of the set ( s = 0 ; p = 1 ; d = 2 ...) \\  +
-lmax = max //l// (angular quantum number) of the set ( s = 0 ; p = 1 ; d = 2 ...) \\ +
-Nexp = number of exponents of the set \\ +
-Ncontr = number of contaction coefficients per angular quantum number \\ +
- +
-As an example:+
  
-<code> +===== Part I: Different basis sets for H and H2 =====
-      2                 2 Sets +
-      1 0 0 1 1         Set 1: lmin=0 ; lmax=0 (→ s functions!) ; 1 exponent ; 1 contraction +
-        0.35 1          exponent1 of  set 1 ; contraction  +
-      1 1 1 1 1         Set 2: lmin=1 ; lmax=1 (→ p functions!) ; 1 exponenet ; 1 contraction +
-        0.6 1           exponent1 of set 2 ;  contraction +
-</code> +
- +
- +
-===== Part I: Create your own basis set for H  =====+
 ==== 1.Step ==== ==== 1.Step ====
  
-Save the following input file. Comment lines are marked with !+Run a calculation with the following input file. Comment lines are marked with !
  
 <code - mybasis.inp >  <code - mybasis.inp > 
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   &DFT   &DFT
-  LSD                                      ! Requests a spin-polarized calculation for an odd number of electrons+  LSD                                      ! Requests a spin-polarized calculation for non paired electrons
   MULTIPLICITY 2                           ! Multiplicity = 2S+1 (S= total spin momentum)   MULTIPLICITY 2                           ! Multiplicity = 2S+1 (S= total spin momentum)
     &POISSON                               ! Solver requested for non periodic calculations       &POISSON                               ! Solver requested for non periodic calculations  
       PERIODIC NONE                               PERIODIC NONE                        
-      PSOLVER  MT                          ! Type of solver+      PSOLVER  WAVELET                     ! Type of solver
     &END POISSON     &END POISSON
     &QS                                    ! Parameters needed to set up the Quickstep framework     &QS                                    ! Parameters needed to set up the Quickstep framework
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   &SUBSYS   &SUBSYS
 +    &TOPOLOGY                              ! Section used to center the molecule in the simulation box. Useful for big molecules 
 +      &CENTER_COORDINATES                  
 +      &END
 +    &END
     &CELL     &CELL
       ABC 10.0 10.0 10.0       ABC 10.0 10.0 10.0
Line 81: Line 54:
     &END COORD     &END COORD
     &KIND H     &KIND H
-     &BASIS                                ! Basis set+     &BASIS                                ! Basis set for H
      2      2
      1 0 0 1 1      1 0 0 1 1
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      0.6 1      0.6 1
      &END      &END
-     POTENTIAL ALL                         ! Potential for all electron calculations+     POTENTIAL ALL                         ! Specifes that the potential is for all electron calculations. 
 +     &POTENTIAL                            ! Usual all electron potential for H  
 +     1    0    0 
 +     0.20000000    0 
 +     &END POTENTIAL
     &END KIND     &END KIND
   &END SUBSYS   &END SUBSYS
 &END FORCE_EVAL &END FORCE_EVAL
  
 +</code>
  
 +==== 2.Step ====
 +Try to change the basis set, and report the obtained energy values for H.
 +After a couple of tries on your own, try to use some of the literature basis sets (given at the end of this exercise).
 +At the end, you should get a table like this :
 +
 +
 +^ Basis set                     ^ Energy  H (Eh)       ^
 +| mybasis (from given input)    | .... |
 +| basis try 1                   | .... | 
 +| basis try 2                   | .... |
 +| ....                          | .... |
 +| pc-0                          | .... | 
 +| pc-1                          | .... |
 +| 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>
 +
 +Repeat the procedure for H2. \\
 +H2 coordinates: 
 +<code>
 +H 0 0 0     
 +H 0.75 0 0   
 </code> </code>
 +
 +<note important> The H2 molecule does not have unpaired electrons. Remember to take out the LSD and MULTIPLICITY keywords. </note>
 +
 +===== Part II: Estimate the binding energy of H2 =====
 +
 +Binding energy: \\ 
 +
 +\[ \sum E_\text{products} -  \sum E_\text{rectants} = E(H_2) - 2 \cdot E(H) \]
 +
 +<note important> The binding energy value is significant only if the same basis is used for both reactants and products. </note>
 +
 +
 +You can now update your table:
 +
 +^ 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 =====
 +
 +- What is the effect of:\\
 +  * 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 =====
 +
 +
 +
 +H  pc-0
 +  2
 +  1  0  0  2  1
 +          4.34480000          0.07929900
 +          0.66049000          0.42422000
 +  1  0  0  1  1
 +          0.13669000          1.00000000
 +
 +H  pc-1
 +  3
 +  1  0  0  3  1
 +         12.25200000          0.02282200
 +          1.86870000          0.15564000
 +          0.41821000          0.48898000
 +  1  0  0  1  1
 +          0.10610000          1.00000000
 +  1  1  1  1  1
 +          1.00000000          1.00000000
 +
 +H  pc-2
 +  6
 +  1  0  0  4  1
 +         75.42300000          0.00240650
 +         11.35000000          0.01848700
 +          2.59930000          0.08974200
 +          0.73513000          0.28111000
 +  1  0  0  1  1
 +          0.23167000          1.00000000
 +  1  0  0  1  1
 +          0.07414700          1.00000000
 +  1  1  1  1  1
 +          1.60000000          1.00000000
 +  1  1  1  1  1
 +          0.45000000          1.00000000
 +  1  2  2  1  1
 +          1.25000000          1.00000000
 +
 +
 +
 +
 +
exercises/2014_ethz_mmm/basis_sets.txt · Last modified: 2020/08/21 10:15 by 127.0.0.1