Keywords

Options:

CARTESIAN | The molecular structure is given in Cartesian coordinates. | ||

ZMATRIX | The molecular structure is defined by a Z-matrix. Equivalent to the option ZMATRIX is the option Z-MATRIX. | ||

MIXED | The first atoms of the molecular structure are defined by Cartesian coordinates and the following ones are defined by a Z-matrix. |

ANGSTROM | Coordinates or bond distances are given in Ångströms. | ||

BOHR | Coordinates or bond distances are given in atomic units. |

The reactant and product geometries for a saddle-point interpolation are read in the keyword bodies of REACTANT and PRODUCT, respectively. Both structures must be local minima on the potential energy surface. If the molecular structures are defined by a Z-matrix, two different VARIABLE definitions are allowed but CONSTANTS must be the same for both REACTANT and PRODUCT . In the following input example, the first variable definition is assigned to the product whereas the second one is assigned to the reactant.

PRODUCT Z-MATRIX ANGSTROM C 6 12.011000 C 1 R1 6 12.011000 O 1 R2 2 A1 RAD 8 15.999400 H 3 R3 1 A2 2 D1 RAD 1 1.007940 H 2 R4 1 A3 3 D2 RAD 1 1.007940 H 1 R5 2 A4 3 D3 RAD 1 1.007940 H 2 R6 1 A5 3 D4 RAD 1 1.007940 # VARIABLES R1 1.33753412 R2 1.35406571 R3 .98316245 R4 1.09714328 R5 1.10195029 R6 1.10140201 A1 126.727334 A2 108.484045 A3 120.171938 A4 122.350600 A5 122.089435 D1 .026953 D2 180.007587 D3 -180.000000 D4 .000000 # # # REACTANT Z-MATRIX ANGSTROM C 6 12.011000 O 1 R1 8 15.999400 C 1 R2 2 A1 RAD 6 12.011000 H 3 R3 1 A2 2 D1 RAD 1 1.007940 H 3 R4 1 A3 2 D2 RAD 1 1.007940 H 3 R5 1 A4 2 D3 RAD 1 1.007940 H 1 R6 2 A5 3 D4 RAD 1 1.007940 # VARIABLES R1 1.21898657 R2 1.48370403 R3 1.10453256 R4 1.11075723 R5 1.11077688 R6 1.13169337 A1 124.467029 A2 111.060189 A3 109.154845 A4 109.123964 A5 120.433172 D1 -.070961 D2 -122.316147 D3 122.144371 D4 179.992103

Constant (frozen) structure parameters must be common to both
reactants and products. Thus, only one set of constant definitions is permitted.
The following input is used for a saddle-point interpolation in which the
positions of `C1` and `C2` remain unchanged.

PRODUCT C1 .000000 .000000 .000000 C2 .000000 .000000 1.508857 H 1.028689 .000000 -.410316 H -1.015045 -.024889 1.940572 H -.529072 -.891070 -.389824 H -.517448 .901443 -.385027 H .544687 .857413 1.954166 H .676484 -.872804 1.873463 SI -.129351 -2.427077 2.452048 H -1.252212 -2.428853 1.388199 H -1.024260 -1.779782 3.537837 # # # REACTANT C1 .000000 .000000 .000000 C2 .000000 .000000 1.508857 H 1.035894 .000000 -.397290 SI .882110 -1.504909 2.206066 H -.504846 -.904544 -.397302 H -.520431 .886537 -.415328 H .492408 .912128 1.916629 H -1.036466 .015343 1.916608 H .883975 -1.510440 3.722866 H .196804 -2.766324 1.714760 H 2.318323 -1.522790 1.716988 # CONSTANTS C XYZ

Please note that the Cartesian coordinates of these two atoms have to be the same in the PRODUCT and REACTANT definitions. In fact, these two structures were optimized with the same constraint. Examples and on page and in the tutorial, show typical inputs for saddle point interpolations.