# Can't use ixc=11 with optdriver=5

**URL:** <https://discourse.abinit.org/t/cant-use-ixc-11-with-optdriver-5/3774>\
**Category:** Response calculations\
**Created:** [November 4, 2025, 4:03pm UTC](https://discourse.abinit.org/t/cant-use-ixc-11-with-optdriver-5/3774 "2025-11-04T16:03:06Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![quantum\_engineer](https://discourse.abinit.org/letter_avatar_proxy/v4/letter/q/8edcca/32.png) [@quantum\_engineer](https://discourse.abinit.org/u/quantum_engineer)\
**Post date:** [November 4, 2025, 4:03pm UTC](https://discourse.abinit.org/t/cant-use-ixc-11-with-optdriver-5/3774/1 "2025-11-04T16:03:06Z")

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Hello,

I’m trying to use the GGA Perdew-Burke-Ernzerhof functional in the context of nonlinear optical properties calculations (so for the last of the datasets, optdriver=5). I haven’t been able to find a way around this error message though:

```auto
 chkint_prt: ERROR -
 Context: the value of the variable ixc is 11.
  The value of the input variable optdriver is 5, while it must be
  different from one of the following: 5
  Action: you should change the input variables optdriver or ixc.

```

Is it simply not possible to combine these?

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**Author:** ![mverstra](https://discourse.abinit.org/user_avatar/discourse.abinit.org/mverstra/32/92_2.png) [@mverstra](https://discourse.abinit.org/u/mverstra)\
**Post date:** [November 5, 2025, 10:01pm UTC](https://discourse.abinit.org/t/cant-use-ixc-11-with-optdriver-5/3774/2 "2025-11-05T22:01:12Z")

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Nope - optdriver 5 is non linear responses with DFPT, and I think the xc contribution has not been implemented with GGA functionals (11 = PBE), though it was being worked on a few years ago.

You can do most things with GGA, then just the last step with LDA. It’s not super clean, but a small approximation in the end. Otherwise, do everything with LDA

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<div class="post-metadata">

**Author:** ![quantum\_engineer](https://discourse.abinit.org/letter_avatar_proxy/v4/letter/q/8edcca/32.png) [@quantum\_engineer](https://discourse.abinit.org/u/quantum_engineer)\
**Post date:** [November 7, 2025, 3:33pm UTC](https://discourse.abinit.org/t/cant-use-ixc-11-with-optdriver-5/3774/3 "2025-11-07T15:33:55Z")

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Thank you for clarifying that 🙂