Keyword PHASE

This keyword permits the explicit definition of molecular orbital phases.
Options:

$<$Integer$>$

Molecular orbital for which an explicit phase convention is defined in the input.

Description:
The molecular orbital (MO) phases are undefined in standard quantum chemical calculations. Therefore, the phase may differ for different diagonalization routines or computational architectures. The keyword PHASE permits the definition of a user-defined phase convention. This is useful if molecular orbitals are plotted for different geometries, e.g. in correlation diagrams, along reaction coordinates, or for a movie from a molecular dynamics run. If the keyword PHASE is specified without any options, then the MO phase is chosen such that the largest molecular orbital coefficient is positive. This choice usually preserves the MO phases for small geometry changes. However, it is not fail-safe. If the molecular orbital phase must be preserved over large geometry changes, an explicit phase convention should be specified with the PHASE keyword combined with some integer numbers. The integer numbers specify the molecular orbitals for which an explicit phase convention is given in the input. The reference MO coefficients are then given in free format, one after the other, respecting the 80 character length limit for each input line, in the body of the keyword PHASE as the following example shows:

 PHASE 21 22
 -0.03127 +0.15629 -0.31825 -0.04906 -0.02041 +0.03267 -0.00927 -0.02741
 +0.02988 +0.00172 +0.00354 -0.00638 +0.00096 +0.00580 +0.00753 +0.00063
 +0.00101 +0.00121 -0.03098 +0.15345 -0.32858 -0.06885 +0.01440 -0.03169
 +0.02076 +0.01737 -0.03349 +0.01821 -0.00553 +0.00307 +0.00218 +0.00501
 +0.00624 +0.00003 +0.00351 -0.00073 -0.01639 +0.08148 -0.16645 -0.09271
 -0.02134 +0.00160 +0.02254 -0.03551 +0.00426 +0.03639 -0.01114 +0.00271
 +0.00982 +0.00644 +0.00203 +0.00302 +0.00077 -0.00037 -0.02184 +0.10920
 -0.21773 -0.10390 +0.02340 -0.00197 -0.03176 +0.03411 -0.00520 -0.04247
 +0.00826 -0.00167 -0.00962 +0.00639 +0.00263 +0.00267 +0.00082 -0.00181
 -0.00645 +0.03270 -0.06593 -0.03674 +0.04837 -0.00504 -0.05537 +0.12202
 -0.02485 -0.12622 +0.03715 -0.00640 -0.03966 -0.00016 -0.00982 +0.00232
 +0.00760 -0.00687 +0.00398 -0.02055 +0.03840 +0.01576 +0.04400 -0.00549
 -0.05095 +0.11616 -0.02418 -0.12269 +0.02478 -0.00534 -0.02588 -0.00075
 +0.01033 -0.00326 -0.00795 +0.01127 -0.03146 +0.15476 -0.35558 -0.21744
 -0.00997 -0.00249 +0.01294 +0.00384 -0.00194 -0.00387 -0.00141 +0.00248
 -0.00098 -0.00335 +0.00100 -0.00271 +0.00256 +0.00016 +0.02919 -0.14448
 +0.32441 +0.19459 -0.00417 -0.00267 +0.01116 +0.01717 -0.00444 -0.01650
 +0.00471 -0.00559 -0.00013 +0.00552 -0.00060 +0.00393 -0.00208 -0.00028

The foregoing input defines explicit phase conventions for MOs 21 and 22. After the diagonalization of the Kohn-Sham matrix, the phases of the new MOs 21 and 22 are obtained by projection with the reference MO coefficients given in the preceding definition.