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Re: [pdDMG] A definition for F_meas_squared for powder data

This seems to have converged on the right definition.
Jim Kaduk
On 2017-03-22 08:11, Robert Von Dreele wrote:> Good> On 3/21/2017 5:43 PM, James Hester wrote:> >> A further refinement to the definition based on feedback:>> >> ;>> The structure factor amplitude for the reflection derived by>> partitioning>> the background-subtracted observed intensity>> _pd_proc.intensity_net between>> reflections in the same proportion as those reflections>> contribute to>> the corresponding background-free calculated point in>> _pd_calc.intensity_net .>> >> ;>> >> On 21 March 2017 at 16:37, James Hester <jamesrhester@gmail.com>>> wrote:>> >> Examination of the GSAS-II GetFobsSq routine suggests that a more>> precise definition would note that the background should be>> subtracted first.   I propose the following revised definition:>> >> ;>> The structure factor amplitude for the reflection derived from>> a powder>> histogram by partitioning observed intensity between peaks at>> each point>> in the same proportion as the model peaks contribute to that>> point.>> Model background is subtracted from both observed and>> calculated values>> before partitioning.>> >> ;>> >> On 13 March 2017 at 15:43, James Hester <jamesrhester@gmail.com>>> wrote:>> >> Dear Powder Dictionary Management Group,>> >> It is now recognised formally that CIF dictionaries may need to>> redefine datanames, and DDLm has been equipped with some facilities>> to handle this.  In the case of the DDLm version of the powder>> dictionary, as far as I can tell the only two datanames from the>> core that are implicitly different are refln.F_complex and>> refln.F_meas_squared.  _refln.F_complex is different purely because>> the phase id has to be considered when performing the calculation>> (unlike in the core case). _refln.F_meas_squared is different both>> because of the need to consider phase_id, but also because the>> procedure for calculating f_meas_squared from the powder histogram>> is completely different to the single crystal case.  Could you all>> please consider what I have written below for F_meas_squared, and>> suggest any improvements. Ideally, the definition text should be>> clear enough for a programmer to implement the calculation.>> >> While I would appreciate feedback from at least some of you, if I>> don't hear from you within a week or so, I will assume that the>> definition below is adequate.>> >> all the best,>> James.>> >> (New cif_pow definitions follow)>> >> save_refln.F_complex>> >> _definition.id [1]                          '_refln.F_complex'>> loop_>> _alias.definition_id>> '_refln.F_complex'>> '_refln_F_complex'>> _definition.update                      2017-03-07>> _description.text>> ;>> The structure factor vector for the reflection calculated from>> the atom site data for the phase given by phase_id.>> ;>> _name.category_id                       refln>> _name.object_id                         F_complex>> _type.purpose                           Measurand>> _type.source                            Derived>> _type.container                         Single>> _type.contents                          Complex>> _enumeration.default                    0.>> loop_>> _method.purpose>> _method.expression>> Definition>> ;>> If (_diffrn_radiation.probe == "neutron")  _units.code =>> "femtometres">> Else If (_diffrn_radiation.probe == "electron") _units.code =>> "volts">> Else                                            _units.code =>> "electrons">> ;>> >> save_>> >> save_refln.F_squared_meas>> >> _definition.id [1]                          '_refln.F_squared_meas'>> loop_>> _alias.definition_id>> '_refln.F_meas'>> '_refln_F_meas'>> _definition.update                      2017-03-07>> _description.text>> ;>> The structure factor amplitude for the reflection derived from>> a powder>> histogram by partitioning observed intensity between peaks at>> each point>> in the same proportion as the model peaks contribute to that>> point.>> ;>> _name.category_id                       refln>> _name.object_id                         F_squared_meas>> _type.purpose                           Measurand>> _type.source                            Derived>> _type.container                         Single>> _type.contents                          Real>> _enumeration.default                    0.>> loop_>> _method.purpose>> _method.expression>> Definition>> ;>> If (_diffrn_radiation.probe == "neutron")  _units.code =>> "femtometres">> Else If (_diffrn_radiation.probe == "electron") _units.code =>> "volts">> Else                                            _units.code =>> "electrons">> ;>> >> save_>> >> -->> T +61 (02) 9717 9907 [2]>> F +61 (02) 9717 3145 [3]>> M +61 (04) 0249 4148>> >> -->> T +61 (02) 9717 9907 [2]>> F +61 (02) 9717 3145 [3]>> M +61 (04) 0249 4148> > --> T +61 (02) 9717 9907> F +61 (02) 9717 3145> M +61 (04) 0249 4148> > _______________________________________________> pdDMG mailing list> pdDMG@iucr.org> http://mailman.iucr.org/cgi-bin/mailman/listinfo/pddmg> >  		 [4]>  		Virus-free. www.avast.com [5]> > > > Links:> ------> [1] http://definition.id> [2] tel:+61%202%209717%209907> [3] tel:+61%202%209717%203145> [4]> https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon> [5]> https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link> _______________________________________________> pdDMG mailing list> pdDMG@iucr.org> http://mailman.iucr.org/cgi-bin/mailman/listinfo/pddmg_______________________________________________pdDMG mailing listpdDMG@iucr.orghttp://mailman.iucr.org/cgi-bin/mailman/listinfo/pddmg

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