# [CP2K-user] What does MULTIPLICITY 0 means?

Thu May 2 09:51:22 UTC 2019

```Thanks Matt,

that was very clarifying :)

tirsdag 30. april 2019 11.22.33 UTC skrev Matt W følgende:
>
>     IF (dft_control%multiplicity == 0) THEN
>          IF (MODULO(nelectron, 2) == 0) THEN
>             dft_control%multiplicity = 1
>          ELSE
>             dft_control%multiplicity = 2
>          END IF
>       END IF
>
> the default zero is just a place holder - gets replaced by 1 or 2 if
> unrestricted and even / odd number of electrons.
>
> Matt
>
> On Tuesday, April 30, 2019 at 10:50:03 AM UTC+1, Torstein Fjermestad wrote:
>>
>> Dear Matt,
>>
>> The part you quote from the manual is very clear.
>> What confuses me is that two lines further down it says "Default value:
>> 0"
>> The multiplicity cannot be zero, so I wonder what the value 0 of the
>> keyword MULTIPLICITY means.
>>
>> Thanks in advance for clarification.
>> Regards,
>> Torstein
>>
>>
>> mandag 29. april 2019 17.19.19 UTC skrev Matt W følgende:
>>>
>>> Hi,
>>>
>>> the online reference manual says
>>>
>>> "MULTIPLICITY {Integer}
>>> Two times the total spin plus one. Specify 3 for a triplet, 4 for a
>>> quartet, and so on. Default is 1 (singlet) for an even number and 2
>>> (doublet) for an odd number of electrons. "
>>>
>>> so [2S + 1] is the multiplicity you give for multiplicity. Where S is
>>> the total spin angular momentum of the system you want to model.
>>>
>>> Matt
>>>
>>>
>>> On Monday, April 29, 2019 at 5:26:24 PM UTC+1, Torstein Fjermestad wrote:
>>>>
>>>> Dear all,
>>>>
>>>> In the Cp2k manual, the explanation for the keyword "MULTIPLICITY" is
>>>> as follows: "*Default is 1 (singlet) for an even number and 2
>>>> (doublet) for an odd number of electrons."*
>>>>
>>>> But then two lines further down, it says: "Default value: 0"
>>>> What does MULTIPLICITY 0 means?
>>>>