Evaluation of properties on rectalinear grids

PSI3 can evaluate a number of one-electron properties on rectalinear 2-D and 3-D grids. In most cases, 3-D grids are utilized. In such cases you only need to specify the appropriate value for GRID and PSI3 will automatically construct a rectalinear 3-D grid that covers the entire molecular system. However, there's no default way to construct a useful 2-D grid in general. Even in the 3-D case you may want to ``zoom in'' on a particular part of the molecule. Hence one needs to be able to specify general 2-D and 3-D grids. In the absence of graphical user interface, PSI3 has a very flexible system for specifying arbitrary rectalinear grids.

The following keywords may be used in construction of the grid:

GRID_ORIGIN = real_vector

A vector of 3 real numbers, this keyword specifies the origin of the grid coordinate system. A rectangular grid box which envelops the entire molecule will be computed automatically if GRID_ORIGIN is missing, however, there is no default for 2-D grids.

GRID_UNIT_X = real_vector

A vector of 3 real numbers, this keyword specifies the direction of the first (x) side of the grid. It doesn't have have to be of unit length. There is no default for 2-D grids.

GRID_UNIT_Y = real_vector

A vector of 3 real numbers, this keyword specifies the direction of the second (y) side. It doesn't have to be of unit length or even orthogonal to GRID_UNIT_X. There is no default for 2-D grids.

GRID_UNIT_XY0 = real_vector

A vector of 2 real numbers, this keyword specifies the coordinates of the lower left corner of a 2-D grid in the 2-D coordinate system defined by GRID_ORIGIN, GRID_UNIT_X, and GRID_UNIT_Y. This keyword is only used to specify a 2-D grid. There is no default.

GRID_UNIT_XY1 = real_vector

A vector of 2 real numbers, this keyword specifies the coordinates of the upper right corner of a 2-D grid in the 2-D coordinate system defined by GRID_ORIGIN, GRID_UNIT_X, and GRID_UNIT_Y. This keyword is only used to specify a 2-D grid. There is no default.

GRID_UNIT_XYZ0 = real_vector

A vector of 3 real numbers, this keyword specifies the coordinates of the far lower left corner of a 3-D grid in the 3-D coordinate system defined by GRID_ORIGIN, GRID_UNIT_X, and GRID_UNIT_Y. This keyword is only used to specify a 3-D grid. There is no default.

GRID_UNIT_XYZ1 = real_vector

A vector of 3 real numbers, this keyword specifies the coordinates of the near upper right corner of a 3-D grid in the 3-D coordinate system defined by GRID_ORIGIN, GRID_UNIT_X, and GRID_UNIT_Y. This keyword is only used to specify a 3-D grid. There is no default.

In addition, the following keywords are useful for evaluation of certain properties on 2-D grids:

GRID_ZMIN = real

This keyword specifies the lower limit on displayed z-values for contour plots of electron density and its Laplacian. Only useful when GRID=2 or GRID=4. Default is 0.0

GRID_ZMAX = real

This keyword specifies the upper limit on displayed z-values for contour plots of electron density and its Laplacian. Only useful when GRID=2 or GRID=4. Default is 3.0

EDGRAD_LOGSCALE = integer

This keyword controls the logarithmic scaling of the produced electron density gradient plot. Turns the scaling off if set to zero, otherwise the higher value - the stronger the gradient field will be scaled. Recommended value (default) is 5. This keyword is only useful when GRID=3.