CP2K Open Source Molecular Dynamics

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howto:kg [2018/12/07 13:11] – 130.60.136.203howto:kg [2018/12/07 13:20] – mpauletti
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 $\displaystyle E_{KS}[P] = T_{S}[P] + E_{ext}[P] + \frac{1}{2} \int\int \frac{\rho(r)\rho(r')}{r-r'}drdr' + E_{XC}[\rho]$. $\displaystyle E_{KS}[P] = T_{S}[P] + E_{ext}[P] + \frac{1}{2} \int\int \frac{\rho(r)\rho(r')}{r-r'}drdr' + E_{XC}[\rho]$.
  
-where $P$ is the reduced one-particle density matrix of the system. In order to arrive at the working equations, one has to introduce the restriction that the external energy functional in the Hohenberg–Kohn energy is linear in the density.+where $P$ is the reduced one-particle density matrix of the system. First of all, it's important to introduce the restriction that the external energy functional in the Hohenberg–Kohn energy is linear in the density.
  
 $\displaystyle E_{ext}^{HK}[\rho_{tot}] = \sum_{A}E_{ext}^{HK}[\rho_{A}]$. $\displaystyle E_{ext}^{HK}[\rho_{tot}] = \sum_{A}E_{ext}^{HK}[\rho_{A}]$.
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 $\displaystyle E_{tot}[{P_{A}}] =\sum_{A}(T_{S}[P_{A}] + E_{ext}[P_{A}]) + E_{hxc}[\rho] + T_{nadd}[{P_{A}}]$. $\displaystyle E_{tot}[{P_{A}}] =\sum_{A}(T_{S}[P_{A}] + E_{ext}[P_{A}]) + E_{hxc}[\rho] + T_{nadd}[{P_{A}}]$.
  
-To avoid the integration of the kinetic energy functional for each subsystem, an atomic potential approximation can be applied. For a local potential one can write:+To avoid the integration of the kinetic energy functional for each subsystem, an atomic potential approximation can be applied. For a local potential:
  
 $\displaystyle T_{nadd} = T_{S}[\rho]−\sum_{A}T_{S}[\rho_{A}] =$\\ $\displaystyle T_{nadd} = T_{S}[\rho]−\sum_{A}T_{S}[\rho_{A}] =$\\
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 $\displaystyle \mu'[\rho_{A}]\rho_{A} = V^{K}[\rho_{A}] \sim \sum_{a \in A}V_{a}^{K}(R_{a})$ $\displaystyle \mu'[\rho_{A}]\rho_{A} = V^{K}[\rho_{A}] \sim \sum_{a \in A}V_{a}^{K}(R_{a})$
  
-and the realization that a typical kinetic energy functional is proportional to $\rho^{5/3}$ leads to a model for the final atomic local potential of the form:+The realization that a typical kinetic energy functional is proportional to $\rho^{5/3}$ leads to a model for the final atomic local potential of the form:
  
 $\displaystyle V_{a}^{K}(R_{a}) = N_{a}\rho_{a}^{2/3}$ $\displaystyle V_{a}^{K}(R_{a}) = N_{a}\rho_{a}^{2/3}$
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 ===== CP2K tutorial ===== ===== CP2K tutorial =====
  
-The division of the total system into subsystems is a critical point, in order to do that properly it is important to tell the CP2K which is the 'minimum unit'. One can use the section TOPOLOGY to define the minimum subsystem:+The division of the total system into subsystems is a critical point, in order to do that properly it is important to specify which is the 'minimum unit', that can be defined in the TOPOLOGY section:
  
 <code> <code>
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 </code> </code>
  
-This strategy is based on the fourth column in the COORD section. At this point the code is able to find the best combination of 'minimum units' through the COLORING_METHOD in order to simplify the calculation. Another suggestion is to run KG calculations using LS_SCF, to do that the SCF section has to be replaced with LS_SCF:+This strategy is based on the fourth column in the COORD section. At this point the code is able to find the best combination of 'minimum units' through the COLORING_METHOD in order to simplify the calculation. Another suggestion is to run KG calculations using LS_SCF, replacing the SCF section with the keyword LS_SCF:
  
 <code> <code>
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 And in the same section others corrections can be added (example: VDW_POTENTIAL).\\ And in the same section others corrections can be added (example: VDW_POTENTIAL).\\
-For the second type of calculation the keyword to select is ATOMIC. This method implies a supplemental atomic potential (create a file which contains all the required potentials). These templates of potentials can be found inside the tests > QS > regtest-kg folder of the CP2K and they can be generated directly from the code (look at tests > ATOM > regtest-pseudo > O_KG.inp). It's important to point out that this method is still in the experimental stage and further investigations are needed.+For the second type of calculation the keyword to select is ATOMIC. This method implies a supplemental atomic potential (create a file which contains all the required potentials). Potential templates can be found inside the "tests > QS > regtest-kg" folder of CP2K and they can be generated directly from the code (look at "tests > ATOM > regtest-pseudo > O_KG.inp"). It's important to point out that this method is still in the experimental stage and further investigations are needed.
  
-<note>Keep in mind: there is also the possibility to avoid completely the $T_{nadd}$ selecting NONE as TNADD_METHOD, but in this way the result of the calculation is going to be wrong, since one term is missing. +<note>Keep in mind: there is also the possibility to completely avoid the $T_{nadd}$ selecting NONE as TNADD_METHOD, but in this way the result of the calculation is going to be wrong, since one term is missing. 
 </note> </note>
howto/kg.txt · Last modified: 2024/01/03 13:20 by oschuett