# 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, 3/77
``and 3/78 are used for this. To quote the relevant section fron the
Users
``References:
`

`*User-Defined Models.* /Gaussian 03 /can use any model
of the general
``form:
`

`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 should
``be used when only local exchange is desired. Any combinable non-local
``exchange functional and combinable correlation functional may be used
``(as listed previously).
`

`You specify the values of the six parameters with various non-standard
``options 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 any
``necessary 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 the
``rest of the keywords are specified, or whether the order and spcing are
``important (as they often are in Gaussian).
`

`I tried to vary the amount of HF exchange, but my calculations kept
``crashing, so I tried the example given in the Users Manual for the
B3LYP
``functional, 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 May
``17 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