UT theoretical chemistry code forum

Hello all,
I know that question was disscussed several times.
I would like to make a modification in CHGCAR file based on the simulations from other method.
I need to understand how charge density is written.
If I have NGX, NGY, NGZ - 52 112 64
Does it mean that first 36 lines will be related to charge density at NGY from 1 to 112 and NGZ from 1 to 64, where NGX=1?
And then the same with NGY=1 and NGZ=1.
Did I understand it correctly?


Thank you!

Here is the description from the vasp guys:

In VASP, the density is written using the following commands in Fortran:

WRITE(IU,FORM) (((C(NX,NY,NZ),NX=1,NGXC),NY=1,NGYZ),NZ=1,NGZC)

The x index is the fastest index, and the z index the slowest index. The file can be read format-free, because at least in new versions, it is guaranteed that spaces separate each number. Please do not forget to divide by the volume before visualizing the file!

Thank you, but I did not fully understand this description.
Could you explain what is C(NX,NY,NZ)?

Thank you very much!

C(NX,NY,NZ) is a 3d fortran array containing the charge density values C at points NX,NY,NZ

Thank you very much!

May I ask what is the pattern in which the data is stored? I understand that it is a 3D Fortran array but why are there 5 columns wrt NX, NY and NZ? Shouldn't there be 3 columns? What are the 2 extra columns for? I know this might be a dumb question, but I request you to please help me with it.

Also, is there any definite methodology to better understand the data we get in a CHGCAR file? I know that Vesta helps us visualize the electron clouds present, but is there any way to better process the 5-column data we get in a CHGCAR file for compact handling and eventually better understanding? For example, I have a CHGCAR file on a 64x64x64 grid. But it is a 5 column dataset as shown in the attached picture. Is there any other way to convert this data into a 3D Matrix of shape (64,64,64)?

If you look at my previous posts in the thread, you can see the format by which this data is written. It is a 64x64x64 data set written with 5 values per line. You could make a 64x64x64 array and read the values back in using the same type of format statement. But generally we read this data into a program such as vesta and visualize the change density, or process it with a program like the bader charge analysis to see how much charge there is on each atom.

Thank you for your reply. That info was very beneficial. But how does VESTA rearrange the data for visualization? I am just trying to understand the ground reality of post processing the CHGCAR data, and will be personally looking for methods to improve it.

There is no post process or rearranging. A statement such as:

READ(IU,FORM) (((C(NX,NY,NZ),NX=1,NGXC),NY=1,NGYZ),NZ=1,NGZC)

will load all the data into the 64x64x64 array C.

Vesta will show either isosurfaces of the data or contour plot slices through the dataset.