CSIZE

[-]csize   LX LY LZ

This keyword allows entering the lengths LX, LY, LZ of the crystal edges, assuming the crystal consists of just one rectangular parallelepiped. Only the relative values of the crystal dimensions are relevant.

Evaluation of crystal cohesive energy of a polar crystal, i.e., a crystal where the unit cell has a nonzero dipole moment.
The problem can be approximately solved by the estimation of two additional terms for the coulombic energy, derived by an integration over a uniform distribution of dipolar unit cells.
The first term, U₂^inner, originates from the inner surface, i.e. the surface of the cutoff sphere for the usual lattice sum (U₁). It does not depend on the crystal shape.
The second term, U₂^outer, originates from the outer surface of the crystal and accounts for the shape dependence of the Coulomb energy.

The results appear in the output file as follows:

 Dipole moment of the unit cell ..... =     55.40 Debye
 ................... components ..... =      0.00     0.00   -55.40 Debye
 Size of the unit cell .............. =     11.91     5.96     5.84 Angstrom
 Size of the crystal ................ =      0.14     0.25     0.45
 Volume of the unit cell ............ =    414.53 Angstrom**3
 Number of molecules in the unit cell =      4

 Correction to the lattice sum ...... =   -675.72 kJ/mol per unit cell
 .................... U2-Inner ...... =   -933.95 kJ/mol per unit cell
 .................... U2-Outer ...... =    258.23 kJ/mol per unit cell

 Correction to the lattice sum ...... =   -168.93 kJ/mol per molecule
 .................... U2-Inner ...... =   -233.49 kJ/mol per molecule
 .................... U2-Outer ...... =     64.56 kJ/mol per molecule

 Total Electrostatic Energy (corrected for crystal polarity and shape)  -301.35 (kJ/mol)
 Total Cohesive Energy (corrected for crystal polarity and shape)        -72.75 (kJ/mol)

"Coulomb Energy of Polar Crystals"
Bouke P. van Eijck and Jan Kroon
J. Phys. Chem B 1997, 101, 1096-1100.