4.6 JECK - Current density tensor point by point

The package provides a basic program (JECK) to calculate the current density tensor and its geometrical derivatives for any grid of points, with freely chosen size and step. This will allow people to use their own methods to obtain the induced current density, derive further quantities and/or apply different visualization techniques. The program can be used interactively through an intuitive interface, which appears after having invoked the program as

prompt> JECK

the interface is displayed on the screen as

Program JECK - Feb 13, 2020 - 13:45
**************************************************
Q =  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
CTOCD =     1
JTERM =     0
CO    =     0.0000000    0.0000000    0.0000000
B     =     0.0000000    0.0000000    1.0000000
MIN   =     1.0000000    1.0000000    1.0000000
MAX   =     1.0000000    1.0000000    1.0000000
STEP  =     1.0000000
H     =     0.0001000
DERIV =     F
R2D   =     F
ALFA  =     2.0000000
VERBO =     F
GR XXXX compute the grid and write it on XXXX file
E to exit

The program reads anything and look for:

• Q

  Select which occupied MO’s are in the sum, it must be followed by $n+1$ values, the first indicating the number of MO’s, the remaining are the MO canonical indices

• CTOCD

  followed by an integer, choses the CTOCD variant 4.12

• JTERM

  0=total, 1=para, 2=dia

• CO

  Common Origin coordinates

• B

  Magnetic field components

• MIN

  Lower grid corner

• MAX

  Upper grid corner

• STEP

  grid step

• H

  incremental for numerical derivatives

• DERIV

  Derivatives on/off

• R2D

  Point to origin displacement on/off

• ALFA

  Costant for GRRO/GPRO

• VERBO

  Verbose printing

• GR

  The grid is computed and written on the XXXX external file

Issuing an empty line makes the grid values to be computed and displayed on the screen. This last way is recommended for very small grids or to check the current density tensor and vector values for one single point, which can be selected entering the three coordinates of MIN equal to those of MAX. Switching on DERIV, analytical and numerical derivatives of the current density vector, for the magnetic field issued through the B parameter, will be displayed. Changing the incremental parameter H one can see how numerical derivatives approaches analytical ones.

For large grids the GR XXXX command generates the XXXX file containing the current density tensor values for each point of the grid. If DERIV is true, then also analytical derivatives of the current density tensor are written on the file, which starts with a brief preamble describing how the data were written and, consequently, how they can be read.