This does sound like a bug. If one of h,k,l are zero then the reflection is centric in P222 so the truncation will be different
I just ran a test on an orthorhombic dataset (P212121) of mine and I do indeed see some strange F=0, sigF>0 reflections, but in Charles Ballard's development version which I've been testing they are OK.
I think you'll have to send your data to Charles Ballard ([log in to unmask]) who is working on ctruncate (or Charles I can send you mine if you like)
Phil
On 10 Feb 2011, at 13:50, Ed Pozharski wrote:
> Excellent point and no, these are not missing reflections. SigF is not
> zero. Also, if I am not mistaken, missing reflections in the MTZ format
> are recorded as NaN.
>
> Ed.
>
> On Thu, 2011-02-10 at 12:17 +0000, Eleanor Dodson wrote:
>> Are you sure these are real FP=0 or reflections which werent measured
>> but have been added for completeness of the h k l list.
>> The check is whether the SigF is also 0.00 - in that case they are
>> genuinely missing..
>>
>> Eleanor
>>
>> On 02/09/2011 11:34 PM, Ed Pozharski wrote:
>>> I observe under some conditions that ctruncate sets some reflections
>>> amplitudes to zero. AFAIU, this should not be happening as even
>>> negative intensities (there are none in this particular dataset) should
>>> produce FP>0 upon truncation.
>>>
>>> 66 out of ~23000 reflections are zeros after ctruncate is applied.
>>> Nothing obvious comes up upon inspecting the corresponding hkl's, except
>>> that one and only one is always zero (sg is P21212, so these are not
>>> systematic absences). One curious thing is that the I/sigma for these
>>> reflections is close to the average I/sigma in the highest resolution
>>> range (but it varies and these reflections are in all resolution
>>> ranges).
>>>
>>> A bug?
>>>
>>
>
> --
> Edwin Pozharski, PhD, Assistant Professor
> University of Maryland, Baltimore
> ----------------------------------------------
> When the Way is forgotten duty and justice appear;
> Then knowledge and wisdom are born along with hypocrisy.
> When harmonious relationships dissolve then respect and devotion arise;
> When a nation falls to chaos then loyalty and patriotism are born.
> ------------------------------ / Lao Tse /
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