howto:static_calculation
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static_calculation [2014/02/03 10:28] – remove spaces in code text oschuett | howto:static_calculation [2020/08/21 10:15] (current) – external edit 127.0.0.1 | ||
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- | ====== | + | ====== |
+ | ===== Introduction ===== | ||
In this tutorial, we are going to show the reader how to perform a | In this tutorial, we are going to show the reader how to perform a | ||
simple static self-consistent Kohn-Sham Density Functional Theory | simple static self-consistent Kohn-Sham Density Functional Theory | ||
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achieve this. | achieve this. | ||
- | ====== Input Files ====== | ||
+ | ===== Input Files ===== | ||
We first look at the input files required for this calculation. The | We first look at the input files required for this calculation. The | ||
necessary input files are: | necessary input files are: | ||
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* '' | * '' | ||
* '' | * '' | ||
- | * '' | + | * '' |
A list of basis set and pseudopotential files may be found in | A list of basis set and pseudopotential files may be found in | ||
- | '' | + | '' |
should cover most of the commonly used elements. The user will, | should cover most of the commonly used elements. The user will, | ||
however, need to produce their own main input file for a given | however, need to produce their own main input file for a given | ||
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&END PRINT | &END PRINT | ||
&END FORCE_EVAL | &END FORCE_EVAL | ||
- | </ | + | </ |
The main sections in the input file are: | The main sections in the input file are: | ||
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PRINT_LEVEL LOW | PRINT_LEVEL LOW | ||
&END GLOBAL | &END GLOBAL | ||
- | </ | + | </ |
We will be doing a static energy and force calculation, | We will be doing a static energy and force calculation, | ||
- | case, we must set [[http:// | + | case, we must set [[http:// |
alias for '' | alias for '' | ||
calculation, | calculation, | ||
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<code cp2k> | <code cp2k> | ||
METHOD Quickstep | METHOD Quickstep | ||
- | </ | + | </ |
The keyword [[http:// | The keyword [[http:// | ||
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&END COORD | &END COORD | ||
&END SUBSYS | &END SUBSYS | ||
- | </ | + | </ |
The subsection [[http:// | The subsection [[http:// | ||
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3 2 2 1 1 | 3 2 2 1 1 | ||
0.4500000000 | 0.4500000000 | ||
- | </ | + | </ |
- | in file '' | + | in file '' |
parameters: | parameters: | ||
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3.25819622 | 3.25819622 | ||
| | ||
- | </ | + | </ |
- | in file '' | + | in file '' |
The subsection [[http:// | The subsection [[http:// | ||
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< | < | ||
< | < | ||
- | </ | + | </ |
where '' | where '' | ||
can be changed by configuring keyword [[http:// | can be changed by configuring keyword [[http:// | ||
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BASIS_SET_FILE_NAME | BASIS_SET_FILE_NAME | ||
POTENTIAL_FILE_NAME | POTENTIAL_FILE_NAME | ||
- | </ | + | </ |
As already mentioned above, the keywords [[http:// | As already mentioned above, the keywords [[http:// | ||
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EPS_DEFAULT 1.0E-10 | EPS_DEFAULT 1.0E-10 | ||
&END QS | &END QS | ||
- | </ | + | </ |
The [[http:// | The [[http:// | ||
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REL_CUTOFF 60 | REL_CUTOFF 60 | ||
&END MGRID | &END MGRID | ||
- | </ | + | </ |
The [[http:// | The [[http:// | ||
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&END XC_FUNCTIONAL | &END XC_FUNCTIONAL | ||
&END XC | &END XC | ||
- | </ | + | </ |
This defines which exchange-correlation density functional we want | This defines which exchange-correlation density functional we want | ||
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&END MIXING | &END MIXING | ||
&END SCF | &END SCF | ||
- | </ | + | </ |
The [[http:// | The [[http:// | ||
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ALGORITHM STANDARD | ALGORITHM STANDARD | ||
&END DIAGONALIZATION | &END DIAGONALIZATION | ||
- | </ | + | </ |
The [[http:// | The [[http:// | ||
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NBROYDEN 8 | NBROYDEN 8 | ||
&END MIXING | &END MIXING | ||
- | </ | + | </ |
The [[http:// | The [[http:// | ||
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&END FORCES | &END FORCES | ||
&END PRINT | &END PRINT | ||
- | </ | + | </ |
tells '' | tells '' | ||
output of the calculation. | output of the calculation. | ||
- | ====== Running the Calculation ====== | ||
+ | |||
+ | ===== Running the Calculation ===== | ||
To run the calculation, | To run the calculation, | ||
package compiled, and with the path to its binaries in the system | package compiled, and with the path to its binaries in the system | ||
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use the MPI version of '' | use the MPI version of '' | ||
< | < | ||
- | mpirun -n 2 -o Si_bulk8.out Si_bulk8.inp & | + | mpirun -n 2 cp2k.popt |
- | </ | + | </ |
in the working directory to run '' | in the working directory to run '' | ||
processes in the background. The '' | processes in the background. The '' | ||
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to start completely from afresh, they must delete '' | to start completely from afresh, they must delete '' | ||
before running a new calculation. | before running a new calculation. | ||
- | ====== Obtaining the Results ====== | ||
+ | ===== Obtaining the Results ===== | ||
After the job has finished, we should obtain the following files: | After the job has finished, we should obtain the following files: | ||
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<code cp2k> | <code cp2k> | ||
SCF_GUESS RESTART | SCF_GUESS RESTART | ||
- | </ | + | </ |
provided that the new calculation shares the same '' | provided that the new calculation shares the same '' | ||
the one that generated the wavefunctions. Otherwise, we would need | the one that generated the wavefunctions. Otherwise, we would need | ||
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*** SCF run converged in 10 steps *** | *** SCF run converged in 10 steps *** | ||
- | </ | + | </ |
The above shows a typical output from a self-consistent Kohn-Sham | The above shows a typical output from a self-consistent Kohn-Sham | ||
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| | ||
SUM OF ATOMIC FORCES | SUM OF ATOMIC FORCES | ||
- | </ | + | </ |
The above shows the results on final energies and forces. | The above shows the results on final energies and forces. | ||
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means the system is more or less relaxed, and its geometry is close | means the system is more or less relaxed, and its geometry is close | ||
to its optimal at ground state. | to its optimal at ground state. | ||
- | ====== Adding Smearing ====== | ||
+ | |||
+ | ===== Adding Smearing ===== | ||
In the example so far, we have not used any smearing on electron | In the example so far, we have not used any smearing on electron | ||
occupation. This is fine for system with a large band gap. However, | occupation. This is fine for system with a large band gap. However, | ||
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ELECTRONIC_TEMPERATURE [K] 300 | ELECTRONIC_TEMPERATURE [K] 300 | ||
&END SMEAR | &END SMEAR | ||
- | </ | + | </ |
This tells '' | This tells '' | ||
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<code cp2k> | <code cp2k> | ||
ADDED_MOS 10 | ADDED_MOS 10 | ||
- | </ | + | </ |
In this example, we have asked '' | In this example, we have asked '' | ||
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Number of orbital functions: | Number of orbital functions: | ||
Number of independent orbital functions: | Number of independent orbital functions: | ||
- | </ | + | </ |
unlike in the previous case with no smearing, now 26 molecular | unlike in the previous case with no smearing, now 26 molecular | ||
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ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): | ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): | ||
- | </ | + | </ |
In the final energy section of the output, we notice that there is | In the final energy section of the output, we notice that there is | ||
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< | < | ||
Electronic entropic energy: | Electronic entropic energy: | ||
- | </ | + | </ |
This should be small for the calculation to be a reliable | This should be small for the calculation to be a reliable | ||
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< | < | ||
Total energy: | Total energy: | ||
- | </ | + | </ |
and the final free energy extrapolated for \(TS \to 0\) is given by: | and the final free energy extrapolated for \(TS \to 0\) is given by: | ||
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< | < | ||
ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): | ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): | ||
- | </ | + | </ |
This is the energy to be quoted as the final result. | This is the energy to be quoted as the final result. |
howto/static_calculation.txt · Last modified: 2020/08/21 10:15 by 127.0.0.1