*From*: "Iraj Daizadeh" <daizadeh (- at -) kappa.ucdavis.edu>*Subject*: FOCK matrix summary.*Date*: Wed, 25 Feb 1998 13:11:59 -0800

Hello. Answers to the questions (shown below) that I have recently posed on the CCL are as follows: Concerning Question 1. The code that I wrote to print out the lower triangular portion of the overlap, and fock matrices (alpha and beta spins) is incorrect in the sense that in G94 the modulus of the matrix element must be greater than a threshold value that is set to Thresh = GFloat(10)**(Key-6) where Key is in most cases 0 (See LTOut in utilam.F [line 47349]). The corrected code is as follows: --------------------------------------------------- NTT = Nbasis*(NBasis+1)/2 Zero = GFloat(0) Thresh = GFloat(10)**(-6) Call FileIO(2,-IRwSao,NTT,V,0) do 211 i=1,NTT If(Abs(V(i)).lt.Thresh) V(i) = Zero 211 write (IOvlp,2010) V(i) C Call FileIO(2,-IRwFA,NTT,V,0) do 212 i=1,NTT If(Abs(V(i)).lt.Thresh) V(i) = Zero 212 write (IUnitFA,2010) V(i) C Call FileIO(2,-IRwFB,NTT,V,0) do 213 i=1,NTT If(Abs(V(i)).lt.Thresh) V(i) = Zero 213 write (IUnitFB,2010) V(i) -------------------------------------------------- I thank Professor Vincenzo Baronem who pointed this out. As to Question 2) I simply calculated: FC = eSC using the output generated by my FORTRAN link in G94. The left and right hand sides of the above equation were equivalent. Prof. Fink and Prof. Stuchebrukhov of UC Davis both pointed out this simple test. Thanks for all those that responded to my queries. Iraj. xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Question 1) --- Hello. I used the following to print out the FOCK (alpha, beta) matrix from Gaussian 94: NTT = Nbasis*(NBasis+1)/2 Call FileIO(2,-IRwFA,NTT,V,0) do 212 i=1,NTT 212 write (IUnitFA,2010) V(i) C Call FileIO(2,-IRwFB,NTT,V,0) do 213 i=1,NTT 213 write (IUnitFB,2010) V(i) Interestingly, when I compared the values generated from this method to the standard Gaussian output; viz., IOp(5/33=5); I found that my numbers were slightly different from theirs. Input Deck: ------------------------------------------------------------------------------- # HF/sto-2g 6d 10f field=z+1000000 geom=coord pop=regular IOp(5/33=5) currents: H2 1+ ion , uhf 1 2 H 0.0 0.0 -4.0 He 0.0 0.0 0.0 H 0.0 0.0 4.0 ------------------------------------------------------------------------------- My output: Gaussian output: -0.528103473677385300000000000000E+00 -0.528103D+00 -0.207077182228009010000000000000E-03 -0.207077D-03 -0.957752692231662150000000000000E+00 -0.957753D+00 0.312943635332713380000000000000E-06 0.000000D+00 -0.257198121834262120000000000000E-03 -0.257198D-03 -0.446838441550770900000000000000E+00 -0.446838D+00 ------------------------------------------------------------------------------ The problem lies in the (1,3) (transposed) element. The number 10^-6 should have been printed out in the standard Gaussian output file; it wasn't. Any information would be greatly appreciated. Since our calculations rely almost completely on these small numbers, this may cause severe problems in our calculations. Thank you in advance for any aid into this matter. xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Question 2) Hello. Is the FOCK matrix that is printed out from Gaussian 94 F'C'=eC' or is it: FC = eSC. The molecular orbital coefficients must be C with eigenvalues e. We need F with C and S. We can do this ourselves but we need to know what 'kind' is the FOCK matrix: viz., F or F'. Thank you. xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx -- Iraj Daizadeh Department of Chemistry University of California One Shields Ave. Davis, CA 95616-5295 Phone: 530.754.8695 Fax: 530.752.8995 email: daizadeh (- at -) kappa.ucdavis.edu