7 - Get density via point charges: match moments & potential

This option works only for CASTEP^3.10 and will only appear if both dipole and quadropule calculations have been performed. The total electronic density is represented by a collection of point charges by matching the exact electrostatic potential (from the PW run) and the calculated (from the previous menu option) dipole and quadrupole moments.

Then, the following menu appears:

..............MENU for SIMULATE ......................

......... Change these parameters if necessary:.......

>>>> Dipole moment (e*A): -40.00000 -40.00000 -41.12812

>>>> Quadrupole moment tensor (e*A*A):

     14.55748 0.00000 3.52430

     0.00000 -31.66499 0.00000

     3.52430 0.00000 17.10751

1. Precision of the summations: 0.100000E-09

2. The center of your box:

   A=> ( 0.000, 0.000, 0.000), fr=> ( 0.000, 0.000, 0.000)

3. Directions of the box sides are: undefined

4. Lengthes of the sides of the box are: undefined

5. Grid for the simulating charge: 5 5 5

   Total number of simulating charges = 27

6. Read the exact potential on the grid <=== undefined!

8. We fit to every 5-th grid point in the potential

9. Calculate simulating charges and put them in the file out.dat_1

---- G e n e r a l   s e t t i n g s -----

An. Coordinates are specified in: <Angstroms>

Co. Show current atomic positions in fractional/Cartesian

--- L e a v e   t h e  m e n u -------

Q. Return to the previous menu

---> Choose the item and press ENTER:

At the top, the calculated dipole and quadrupole moments are shown. What is done is this: the charge density in the cell is simulated by a collection of point charges which are positioned at the fine grid to be chosen in the menu (options 5) within a box also to be specified (options 2-4). The box should contain the whole molecule. The charges are chosen to match the exact potential in the cell region which is outside the molecule (i.e. outside the box). The exact potential is be read in separately in option 6. Then, the positions and the values of charges that match both the potential and the dipole and quadrupole moments of the molecule are witten to the output file shown in 9.