Point Group Symmetry

To speed up the calculation, one can take advantage of symmetries in the system. To that effect the keyword POINT GROUPPOINT GROUP has to be added to the &SYSTEMcpmdsec:SYSTEM section, e.g. in the form of

 POINT GROUP
  AUTO

with automatic detection of the point group. As a result we get some additional output displaying the results of the symmetry detection.

 AUTOMATIC DETERMINATION OF THE POINT GROUP:

 THE CRYSTAL SYSTEM IS CUBIC WITH  4 OPERATIONS:
    1            2[ 0 1 0]   -2[ 1 0 0]   -2[ 0 0 1]
 THE SPACE GROUP OF THE CRYSTAL IS SYMMORPHIC
 THE POINT GROUP OF THE CRYSTAL IS  2/m(c2h)           [INDEX= 5]
 NUMBER OF PRIMITIVE CELL:                                      1

 TRANSLATION VECTORS:
 TVEC(  1): [ 0.000,  0.000,  0.000]

 SYMMETRY UNIQUE (INEQUIVALENT) ATOMS:                          2
 INDEXES:   1   2
 REQUIRED PRECISION FOR SYMMETRY:                        1.00E-06

 NUMBER OF IRREDUCIBLE REPRESENTATIONS:                         4
 DIMENSION OF IR:                                      1  1  1  1

As a consequence the code will skip the finite difference steps for the second hydrogen atom, since it is related to the other through c2h symmetry.

 **** ATOM=      3       H       X    DISPLACEMENT=  -1.00000E-02
 ITER=    14         ENERGY=                       -17.1989178081
 TCPU=     0.00      GRADIENT=                          0.000E+00

 **** ATOM=      3       H       X    DISPLACEMENT=   1.00000E-02
 ITER=    14         ENERGY=                       -17.1989178081
 TCPU=     0.00      GRADIENT=                          0.000E+00

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