A error about:tddft diagon: A-B is not positive-definite; try TDA


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Dear Sir

  I want to calculate a spin-restricted TDDFT calculation of singlet excitation energies for the Au8Si cluster molecule at the pbe0/CRBNBL,but it is wrong with "tddft_diagon: A-B is not positive-definite; try TDA". 

The input file:
echo
start Au8Si_dft
                                                   
title "tutorial demonstrating the use of a ecp"
                                                   
charge 0
                                                   
geometry
 Au  1.3530131728	 0.3937507589	-3.7680248656     
Au 1.3530131728 0.3937507589 3.7680248656
Au -0.8186024100 -1.1293885446 0.0000000000
Au 1.5493608399 -0.7208906102 -1.3333655972
Au -0.6002686208 1.0471335408 -2.0218426047
Au -0.6002686208 1.0471335408 2.0218426047
Au 1.5493608399 -0.7208906102 1.3333655972
Au -3.4637765897 -0.5350566117 0.0000000000
Si -1.8715419611 1.3113802577 0.0000000000
end
                                                   
basis
Si S
    11.0700000              1.0000000              
Si S
     1.2210000              1.0000000              
Si S
     0.2473000              1.0000000              
Si S
     0.0862400              1.0000000              
Si P
     6.6710000              1.0000000              
Si P
     2.1200000              1.0000000              
Si P
     0.2975000              1.0000000              
Si P
     0.0886700              1.0000000              
Au S
     2.4651000              1.0000000              
Au S
     1.9431000              1.0000000              
Au S
     0.5613000              1.0000000              
Au S
     0.1452000              1.0000000              
Au S
     0.0503900              1.0000000              
Au P
     3.5306000              1.0000000              
Au P
     2.6122000              1.0000000              
Au P
     0.9813000              1.0000000              
Au P
     0.4266000              1.0000000              
Au P
     0.1475000              1.0000000              
Au D
     1.3366000              1.0000000              
Au D
     0.5035000              1.0000000              
Au D
     0.1940000              1.0000000              
Au D
     0.0756000              1.0000000              
end
                                                   
ECP
Si nelec 10
Si ul
2 1.62109999 -0.67587200
2 4.53210002 -6.72859800
2 13.20760000 -19.62386489
1 39.96990013 -6.58675301
Si S
2 1.86890000 -54.56442690
2 2.11390001 146.37274933
2 2.45269999 -88.33109474
1 3.88029999 6.76354098
0 2.56439999 3.11288401
Si P
2 2.47999999 116.56166363
2 2.97729999 -224.59841347
2 3.77399999 138.22863007
1 5.56639999 2.85250399
0 10.31330001 5.07075799
Au nelec 60
Au ul
2 2.07069993 -0.90820301
2 5.28779984 -13.97286034
2 13.28610039 -78.04593658
2 38.22499847 -150.67013550
2 120.82949829 -433.79324341
1 415.27328491 -53.92461777
Au S
2 2.81620002 -45.11843872
2 3.12030005 109.24782562
2 4.16239977 -184.75865173
2 6.38819981 436.13348389
2 10.11999989 -356.46279907
2 17.04649925 411.84240723
1 50.50329971 31.95258903
0 39.28239822 6.79167795
Au P
2 2.41569996 -30.62415695
2 2.79209995 101.11966705
2 3.67700005 -210.51446533
2 5.37360001 435.37313843
2 8.36999989 -396.14450073
2 13.32330036 368.87313843
1 37.15980148 31.59367371
0 37.42219925 5.83880520
Au D
2 1.87390006 -34.10911942
2 2.11870003 100.58750153
2 2.69359994 -172.30566406
2 3.81640005 290.82238770
2 5.69740009 -292.96429443
2 8.62959957 275.67791748
1 19.68020058 30.37005806
0 25.98660088 7.86203289
Au F
2 1.43149996 40.06137466
2 1.65450001 -128.38630676
2 2.16300011 247.77139282
2 3.08719993 -342.54879761
2 4.65740013 359.27548218
2 6.90420008 -182.27494812
1 10.14780045 53.49130630
0 47.02579880 4.28036213
END
                                                   
dft
 xc b3lyp                                          
mult 1
iterations 500
end
tddft
 NROOTS 3                                          
singlet
notriplet
maxiter 1000
END
                                                   
task tddft energy


   Best regards

Forum Vet
add CIS keyword to tddft field
Hugh,
you need to add the CIS keyword in the TDDFT field as explained at

http://nwchemgit.github.io/index.php/Release61:Excited-State_Calculations#CIS_and_RPA_--_the...

Cheers, Edo

Forum Regular
Hi Hugh,

It could also be that you are not at the true ground state. If you use the CIS which is also called the Tamm-Dancoff approximation, the B matrix is set to 0. But you might notice negative excitation energies because the A-B condition is no longer present. I suggest you carefully examine your ground state calculation.

Best regards,
-Niri

niri.govind@pnl.gov


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