Convergence problem with tiny molecule


Click here for full thread
Just Got Here
Hi! I'm pretty new to computational chemistry. I'm trying to solve a tiny crystal of Titanium nitride which fails to converge..

I'd be glad to post the full output here, but I've only added a tiny portion here. Any insight appreciated.. Thanks in advance..
The input deck is
echo

restart molecule
memory 4000 mw

title "Base test for TiN"

charge 0

geometry units angstroms print xyz
  N 0.000 0.000 0.000
 Ti 0.000 0.000 2.053
  N 0.000 2.053 2.053
 Ti 0.000 2.053 0.000
 Ti 2.053 0.000 0.000
  N 2.053 0.000 2.053
 Ti 2.053 2.053 2.053
  N 2.053 2.053 0.000
end

basis
 * library 6-31G*
end


task scf optimize
~                    


it ends up with noticeable problems

here...

                NWChem Input Module
                                -------------------


                                 Base test for TiN
                                 -----------------

 Scaling coordinates for geometry "geometry" by  1.889725989
 (inverse scale =  0.529177249)

  WARNING: autosym failed! 

          ------
          auto-z
          ------
  autoz: excessive number of variables                   312                   18

 AUTOZ failed to generate good internal coordinates.
 Cartesian coordinates will be used in optimizations.



here,

#quartets = 2.865D+06 #integrals = 1.742D+08 #direct =  0.0% #cached =100.0%


File balance: exchanges=     9  moved=   126  time=   0.0


              iter       energy          gnorm     gmax       time
             ----- ------------------- --------- --------- --------
                 1    -3611.0127873989  3.27D-02  2.76D-03     10.0
  ga_iter_lsolve: convergence stagnant ... aborting solve

 Disabled NR: increased maxiter to  40

                 2    -3611.0128589916  1.53D-02  2.41D-03     16.5
                 3    -3611.0129153319  2.23D-02  2.48D-03     18.3
                 4    -***************  2.27D-02  2.21D-03     20.2
                 5    -3611.0131005953  2.95D-02  2.26D-03     22.1
                 6    -3611.0132604816  3.72D-02  5.25D-03     23.9
                 7    -3611.0135057812  4.73D-02  4.67D-03     26.1
                 8    -3611.0140033884  7.32D-02  7.09D-03     28.1
                 9    -3611.0144080019  4.50D-02  4.66D-03     29.1
                10    -3611.0149139866  5.02D-02  3.87D-03     31.1
                11    -3611.0151837735  3.65D-02  4.53D-03     32.1
                12    -3611.0154382734  4.22D-02  4.24D-03     34.1
                13    -3611.0156509728  4.53D-02  4.05D-03     35.1
                14    -3611.0159550975  4.94D-02  4.24D-03     37.1
                15    -3611.0163239377  6.48D-02  5.27D-03     39.1
                16    -3611.0167088673  5.12D-02  3.57D-03     41.2
                17    -3611.0170517737  4.84D-02  3.61D-03     43.1
                18    -3611.0172972597  4.39D-02  4.15D-03     45.0
                19    -3611.0175607504  3.92D-02  3.44D-03     47.0
                20    -3611.0177757784  3.39D-02  2.95D-03     49.0
                21    -3611.0179212532  3.28D-02  3.04D-03     50.9
                22    -3611.0181047710  3.54D-02  3.65D-03     52.8
                23    -***************  3.44D-02  3.19D-03     54.9
                24    -3611.0183983684  2.41D-02  2.34D-03     55.8
                25    -3611.0184835141  2.50D-02  2.96D-03     57.7
                26    -3611.0185633248  2.41D-02  2.43D-03     58.7
                27    -3611.0186204888  1.95D-02  1.68D-03     60.8
                28    -3611.0186737605  2.58D-02  2.67D-03     62.7
                29    -3611.0187208995  1.87D-02  1.53D-03     64.7
                30    -3611.0187506432  1.52D-02  1.54D-03     66.6
                31    -3611.0187699380  1.21D-02  8.77D-04     68.5
                32    -3611.0187807574  8.19D-03  6.84D-04     70.5
                33    -3611.0187879746  7.58D-03  8.32D-04     71.4
                34    -3611.0187930970  6.08D-03  4.72D-04     73.3
                35    -3611.0187971029  7.77D-03  8.64D-04     75.2
                36    -3611.0188019051  5.76D-03  4.27D-04     77.2
                37    -3611.0188046640  4.39D-03  3.22D-04     78.2
                38    -3611.0188070262  4.16D-03  3.78D-04     80.2
                39    -3611.0188089719  3.98D-03  2.70D-04     82.2
                40    -3611.0188104442  3.63D-03  3.43D-04     84.1

      Calculation failed to converge
      ------------------------------





and
Mulliken analysis of the total density
  --------------------------------------

    Atom       Charge   Shell Charges
 -----------   ------   -------------------------------------------------------
    1 N    7     8.18   2.00  0.75  2.19  1.17  2.09 -0.01
    2 Ti  22    20.93   2.00  2.00  6.00  2.04  6.04  0.09  0.41  0.10  0.13  1.05  1.09 -0.03
    3 N    7     7.93   2.00  0.79  2.10  1.15  1.90 -0.01
    4 Ti  22    20.93   2.00  2.00  6.00  2.04  6.04  0.09  0.41  0.10  0.13  1.05  1.09 -0.03
    5 Ti  22    20.73   2.00  2.00  6.00  2.10  6.10  0.14  0.34  0.27 -0.03  0.77  1.14 -0.08
    6 N    7     8.18   2.00  0.75  2.19  1.17  2.09 -0.01
    7 Ti  22    20.94   2.00  2.00  6.00  2.04  6.04  0.09  0.42  0.11  0.13  1.05  1.09 -0.04
    8 N    7     8.18   2.00  0.75  2.19  1.17  2.09 -0.01

       Multipole analysis of the density wrt the origin
       ------------------------------------------------

     L   x y z        total         open         nuclear
     -   - - -        -----         ----         -------
     0   0 0 0     -0.000000      0.000000    116.000000

     1   1 0 0     -0.035001      0.000000      0.000000
     1   0 1 0      0.091786      0.000000      0.000000
     1   0 0 1      0.076219      0.000000      0.000000

     2   2 0 0    -63.918580      0.000000    436.489266
     2   1 1 0     -5.961029      0.000000      0.000000
     2   1 0 1     -5.895635      0.000000     -0.000000
     2   0 2 0    -64.033200      0.000000    436.489266
     2   0 1 1      6.168750      0.000000      0.000000
     2   0 0 2    -64.011313      0.000000    436.489266


 Parallel integral file used    3992 records with       0 large values

 scf_gradient: scf energy failed        0
 ------------------------------------------------------------------------
 scf_gradient: scf energy failed        0
 ------------------------------------------------------------------------
 scf_gradient: scf energy failed        0
 ------------------------------------------------------------------------
 This type of error is most commonly associated with calculations not reaching convergence criteria
 ------------------------------------------------------------------------
 scf_gradient: scf energy failed        0