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exercises:common:chg

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exercises:common:chg [2022/10/18 15:01] – jglanexercises:common:chg [2023/12/04 13:47] – fnunes
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 It requires three single-point calculations of system AB, A, and B to print the [[https://manual.cp2k.org/cp2k-2022_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/E_DENSITY_CUBE.html|electron density]] or [[https://manual.cp2k.org/cp2k-2022_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/TOT_DENSITY_CUBE.html|total density]]. It requires three single-point calculations of system AB, A, and B to print the [[https://manual.cp2k.org/cp2k-2022_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/E_DENSITY_CUBE.html|electron density]] or [[https://manual.cp2k.org/cp2k-2022_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/TOT_DENSITY_CUBE.html|total density]].
 +
 +One can use [[https://www.cp2k.org/tools:cubecruncher | Cubecruncher]] to manipulate the CUBE files.
 +
 +<code>
 +cubecruncher.x -i AB.cube   -subtract A.cube -o AB_A.cube
 +cubecruncher.x -i AB_A.cube -subtract B.cube -o chg_dif.cube
 +</code>
 +
 +This type of analysis is also useful in the case of time-dependent calculations. In this case, the difference would be taken over time, with respect to some reference snapshot (e.g. ground state). 
 +
 +$\Delta \rho (t-t_0) = \rho(t) - \rho(t_0)$,
 +
 +where $\rho(t)$ is the electron density at time $t$, and $\rho(t_0)$ is the reference electron density.
 +
 +<code>
 +cubecruncher.x -i elec_dens_t.cube -subtract elec_dens_t0.cube -o difference_t-t0.cube
 +</code>
exercises/common/chg.txt · Last modified: 2023/12/04 13:49 by fnunes