# Write density on grid of my choice

Sascha Brück bru... at iis.ee.ethz.ch
Tue Apr 15 15:11:44 CEST 2014

```Hi,

in cp2k, i can write out the density into a cube file, but it will be
evaluated at grid points computed by cp2k. If I like to use my own grid
with different points where I want to evaluate the density, is there a way

If not, it should be easy to evaluate the density by oneself by just
summing the density matrix and the basis functions

rho(x_grid,y_grid,z_grid)=sum_{i,j} P_{i,j} * phi_i
(x_grid-x_atom(i),y_grid-y_atom(i),z_grid-z_atom(i)) * phi_j
(x_grid-x_atom(j),y_grid-y_atom(j),z_grid-z_atom(j))

where phi_i (x,y,z)=norm_i * pow(x,lx_i) * pow(y,ly_i)* pow(z,lz_i) * exp(
-alpha_i*(x^2+y^2+z^2));

all coordinates are in bohr radius and alpha_i is from the basis file and
the angular momenta are ordered like 1s 1px 1py 1pz 2s 2px 2py 2pz ...

Is this formula right? Or do I have to transform to spherical basis
functions (even for s and p)? How do i compute the norm?

Best regards
Sascha
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