fatal error in geom calc dihedral

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I calculate CDFT of a moleculear of 62 atoms , fatal error in geom_calc_dihedral occured as follows


==============================================================================
                            internuclear dihedral angles
------------------------------------------------------------------------------
center 1 | center 2 | center 3 | center 4 | degrees
------------------------------------------------------------------------------
19 H | 1 C | 5 N | 2 C | 179.93
... ...
   6 Pd       |   7 N        |  11 C        |   5 N        |     0.06
fatal error in geom_calc_dihedral
mbaxbc 5.950284209926354E-004
mcbxcd 13.9845127888136
a coordinates 15.2677959032440 9.000000000090243E-006
-8.999999999972690E-006
b coordinates 10.7583661605949 -1.699999999990976E-005
2.100000000002731E-005
c coordinates 7.13864542636145 -1.509999999999098E-004
1.130000000000273E-004
d coordinates 10.0988601606376 -3.03333667777368
2.39276801962222
angle abc 179.997911359031
angle bcd 52.5417216081486
angle abd 99.6877275510057
angle acd 52.5405723513803
please report this data to:
nwchem-users@emsl.pnl.gov
------------------------------------------------------------------------
geom_print_dih:geom_calc_dih death 911
------------------------------------------------------------------------
------------------------------------------------------------------------
current input line :
106: task dft optimize
------------------------------------------------------------------------
------------------------------------------------------------------------
There is an error related to the specified geometry
------------------------------------------------------------------------
For more information see the NWChem manual at
http://www.nwchem-sw.org/index.php/NWChem_Documentation


For further details see manual section: 




0:0:geom_print_dih:geom_calc_dih death:: 911
(rank:0 hostname:linux-qji0 pid:11367):ARMCI DASSERT fail. armci.c:ARMCI_Error():260 cond:0

Does anybody help me?

Just Got Here
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Posts 4
Fatal error in geom_calc_dihedral
Hi Zhang,

The problem is that in your case the particular dihedral angle is undefined. The reason is that if you have atoms A-B-C-D then the dihedral angle is defined as the angle between the planes defined by A-B-C and B-C-D. These planes are uniquely defined as long as the atoms A-B-C and B-C-D are not on a line. If they are, however, on a single line there is no unique definition of the dihedral angle. If you check the coordinates print below (a coordinates through to d coordinates ) then you'll see that the atoms A-B-C are almost exactly on a line. Hence the error message you are getting.

This explains what the error is but not why you are getting it. Your geometry optimization must somehow be using internal coordinates (maybe forced by constraints on the geometry) that become ill defined along the optimization pathway. This is very likely highly case specific. So you may want to have a look at the geometry and maybe the optimization pathway that got you to this point. This should give you some information as to why you are hitting this problem.

Best wishes,

    Huub


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