CRYSTAL06 versus CRYSTAL03

Input

CRYSTAL06 wave function calculation (program crystal) input now consists of 3 blocks, instead of 4:

geometry input:
geometry optimization new package and keyword OPTGEOM;
basis set input;
hamiltonian & SCF The shrinking factors to define Monkhorst (IS) and Gilat (ISP) net are entered after a new keyword SHRINK (3rd input block):
```
SHRINK
IS ISP
```

CRYSTAL06 properties calculation (program properties) NEWK input is modified:

NEWK
IS ISP
IFE NUMPRT (see User's Manual)

Output

Wave function data written in file fort.9 and fort.98 by crystal or properties are different. Data computed with CRYSTAL03 can not be read by CRYSTAL06.

Some records are written in file fort.25 by CRYSTAL06 properties in a different format.

Keywords BAND DOSS ECHG

BAND-DOSS-MAPN
1st record format: A3,I1,A4,2I5,1P,(3E12.5) - it was A3,I1,A4,2I4,1P,(3E12.5)

DOSS and BAND:
3rd record format: 6I5 it was 6I3

Algorithms and numerical implementation

The most important improvements in algorithms and numerical implementation are:

Screening of the bielectronic integrals
A few modifications in the screening of terms of infinite sums may affect the value of total energy slightly in some cases. In the calculation of the Coulomb and exchange series the main selection criteria for the integrals to be computed are based on the overlap between shells of a pair. However, a shell consists of atomic orbitals resulting from a contraction of gaussian functions and some of these integrals may give negligible contributions to the sum. For this reason, an additional screening operates a finer selection of the integrals to be computed which is based on every single gaussian exponent. With the default setting of tolerances (TOLINTEG) a change in the geometry of a system may affect this latter selection and introduce small artificial discontinuities in the potential energy surface. This happened in CRYSTAL03, even if the FIXINDEX option, aiming at smoothing potential energy surfaces, was active. This problem has been fixed in CRYSTAL06. That implies that this new release may produce slightly different results at some geometry of a system when using FIXINDEX, for example during geometry optimizations.
DFT grids for numerical integration
In the generation of the grids used for the numerical integration of the exchange-correlation density functional a screening of the grid points based on their geometrical weight and the parameter TOLGRID leads to a beneficial reduction of the grid size. These geometrical weights include a multiplicity factor associated with the symmetry properties of each point. This factor was erroneously taken into account during the selection of the grid points in CRYSTAL03. Such inconsistency has been removed from CRYSTAL06. This may result in slight changes in the total energy per cell.

New features keywords are entered in geometry input block: full optimization (OPTGEOM, and frequency calculation (FREQCALC). They are presented in new sections.

Test cases

crystal03 versus crystal06 total energies (hartree)

             crystal03         crystal06        diff
 TEST 0   -110.7649354548   -110.7649354541  -7.6E-10
 TEST 1    -39.7267242377    -39.7267242374  -2.8E-10
 TEST 2   -223.7874757199   -223.7874756819  -3.8E-08
 TEST 3   -893.8746580039   -893.8746580004  -3.4E-09
 TEST 4  -1400.1776585267  -1400.1776585535   2.7E-08
 TEST 5    -74.8333583547    -74.8333583570   2.3E-09
 TEST 6    -58.4208255976    -58.4208255980   3.6E-10
 TEST 7  -2800.7355953670  -2800.7355953744   7.4E-09
 TEST 8   -571.3207540598   -571.3207540594  -4.2E-10
 TEST 9    -29.2566111179    -29.2566111179   0.0E+00
 TEST10   -577.8265583366   -577.8265583285  -8.0E-09
 TEST11   -274.6641530285   -274.6641530559   2.7E-08
 TEST12   -447.6810664605   -447.6810664796   1.9E-08
 TEST13    -23.9856901336    -23.9856901143  -1.9E-08
 TEST14   -159.6970601311   -159.6970601598   2.9E-08
 TEST15  -5229.8366028287  -5229.8366027787  -5.0E-08
 TEST16  -2995.2869386925  -2995.2869386582  -3.4E-08
 TEST17  -2674.3752958292  -2674.3752958032  -2.6E-08
 TEST18   -679.2766564865   -679.2766564082  -7.8E-08
 TEST19   -223.8070778082   -223.8070777860  -2.2E-08
 TEST20    -89.9552982254    -89.9552981100  -1.2E-07
 TEST21   -447.5749512396   -447.5749511978  -4.2E-08
 TEST22   -460.7186326899   -460.7186326563  -3.4E-08
 TEST23     -8.0613160104     -8.0613160317   2.1E-08
 TEST24  -1400.1776187881  -1400.1776188146   2.6E-08
 TEST25    -74.8442039897    -74.8442039913   1.5E-09
 TEST26    -58.4208255857    -58.4208255860   3.1E-10
 TEST27  -2800.7355409765  -2800.7355409839   7.4E-09
 TEST28     -8.0429325843     -8.0429330764   4.9E-07
 TEST29  -2047.6430863277  -2047.6430862965  -3.1E-08
 TEST30   -109.0441465735   -109.0441458665  -7.1E-07
 TEST31  -4095.2867581984  -4095.2867581744  -2.4E-08
 TEST32    -92.1408103960    -92.1408103960   0.0E+00
 TEST33    -92.1416132011    -92.1416129818  -2.2E-07
 TEST34  -1117.5230436301  -1117.5230436113  -1.9E-08
 TEST35   -936.5017524997   -936.5017511475  -1.4E-06
 TEST36   -112.5648953627   -112.5648952230  -1.4E-07
 TEST37  -3028.3682393194  -3028.3682392875  -3.2E-08
 TEST38  -2279.1395902355  -2279.1395902381   2.6E-09