DFT functionals with varying amounts of HF exchange

From: Heidi Rohwer <heidi.rohwer :: aci.uni-heidelberg.de>
Subject: DFT functionals with varying amounts of HF exchange
Date: Tue, 17 May 2005 11:05:20 +0200

 Hello All

I am trying to do some DFT calculations with the BLYP functional,varying the amount of HF exchange using the Gaussian IOps.According to the Gaussian 03 Users Reference, the the IOps 3/76, 3/77and 3/78 are used for this. To quote the relevant section fron the UsersReferences:

*User-Defined Models.* /Gaussian 03 /can use any model of the generalform:
 
P_2 E_X ^HF + P_1 (P_4 E_X ^Slater + P_3 N E_x ^non-local ) + P_6 E_C^local + P_5 N E_C ^non-local
 
The only available local exchange method is Slater (*S*), which shouldbe used when only local exchange is desired. Any combinable non-localexchange functional and combinable correlation functional may be used(as listed previously).
 
You specify the values of the six parameters with various non-standardoptions to the program:
    *
       *IOp(3/76*=/mmmm//m//nnnn//n/) sets P_1 to/ mmmmm//10000 and P_2
       to /nnnnn//10000. P_1 is usually set to either 0.0 or 1.0,
       depending on whether an exchange functional is desired or not,
       and any scaling is accomplished using P_3 and P_4 .
    *
       *IOp(3/77*=/mmmm//m//nnnn//n/) sets P_3 to /mmmmm//10000 and P_4
       to /nnnnn//10000.
     * *IOp(3/78*=/mmmm//m//nnnnn/) sets P_5 to /mmmmm//10000 and P_6
       to /nnnnn//10000.
 
For example,* IOp(3/76=1000005000*) sets P_1 to 1.0 and P_2 to 0.5.Note that all values must be expressed using five digits, adding anynecessary leading zeros.
 
Here is a route section specifying the functional corresponding to the*B3LYP* keyword:
 # BLYP IOp(3/76=1000002000) IOp(3/77=0720008000) IOp(3/78=0810010000
 

However, the Users Reference does not say where the basis set or therest of the keywords are specified, or whether the order and spcing areimportant (as they often are in Gaussian).

I tried to vary the amount of HF exchange, but my calculations keptcrashing, so I tried the example given in the Users Manual for the B3LYPfunctional, using the following input:

#BLYP/6-31G(d) IOp(3/76=1000002000) IOp=(3/77=0720008000)IOp=(3/78=0810010000) Opt

 But the calculation crashes with the error message:

 Will use up to 2 processors via shared memory.
 Default route: MaxDisk=230000000 SCF=Tight MP2=FullDirect
 ----------------------------------------------------------------------
 #BLYP/6-31G(d) IOp(3/76=1000002000) IOp=(3/77=0720008000) IOp=(3/78=08
 10010000) Opt
 ----------------------------------------------------------------------
 QPERR --- AN AMBIGUOUS KEYWORD WAS DETECTED.
 OP(3/76=1000002000) IOP=(3/77=0720008000
 '
 Last state="GCL"
 TCursr= 88 LCursr= 36

Error termination via Lnk1e in /work/soft/g03/p6/g03/l1.exe at Tue May17 10:46:43 2005.

 Job cpu time: 0 days 0 hours 0 minutes 0.2 seconds.
 File lengths (MBytes): RWF= 7 Int= 0 D2E= 0 Chk= 1 Scr= 1

 I tried an alternative input, specifying the basis set after the IOps:

#BLYP IOp(3/76=1000002000) IOp=(3/77=0720008000)IOp=(3/78=0810010000)/6-31G(d) Opt

 But I get the same error message as before.
 Any help solving this problem would be much appreciated!
 Regards
 Heidi Rohwer