Discussion List Archives

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Some additional data items for the REFINE category

  • To: Multiple recipients of list <coredmg@iucr.org>
  • Subject: Some additional data items for the REFINE category
  • From: Brian McMahon <bm@iucr.org>
  • Date: Wed, 9 May 2001 09:58:01 +0100 (BST)
Dear Colleagues

I wish to circulate some proposals for additions to the core dictionary.
I shall treat them in three separate mailings.

This first block is a small number of additional data items that Gotzon
found useful for his modulated structures dictionary, but which have wider
application. These were posted some months ago, and I should have circulated
them with the last round of Core discussions; I can only apologise to Gotzon
that I clean forgot to do so.

Please read and comment at an early opportunity; it is a useful sign of the
vitality of the Core dictionary if we can add entries expeditiously whenever
a well-defined need arises.

Best regards
Brian


############
## REFINE ##
############

data_refine_ls_F_calc_accuracy
    _name                        '_refine_ls_F_calc_accuracy'
    _category                    refine
    _type                        numb
    _enumeration_range           0.0:
    _definition
;              The estimated accuracy in electrons (for X-ray diffraction)
               reached during the evaluation of the structure factor given
               by _refine_ls_F_calc_formula following the method outlined
               in _refine_ls_F_calc_details.
;

data_refine_ls_F_calc_details
    _name                        '_refine_ls_F_calc_details'
    _category                    refine
    _type                        char
    loop_ _example               'Gaussian integration using 16 points'
;              Bessel functions expansion up to 5th-order. Bessel
               functions estimated accuracy: better than 0.001
;

    _definition
;              Details concerning the evaluation of the structure factor given
               by _refine_ls_F_calc_formula.
;

data_refine_ls_F_calc_formula
    _name                        '_refine_ls_F_calc_formula'
    _category                    refine
    _type                        char
    _definition
;              Analytical expression used to calculate the structure factor.
;

data_refine_ls_restrained_wR_factor_all
    _name                        '_refine_ls_restrained_wR_factor_all'
    _category                    refine
    _type                        numb
    _enumeration_range           0.0:
    _definition
;              The weighted residual factors for all reflections used in the
               refinement, including explicitly the restraints applied in the
               least-squares process. The reflections also satisfy the
               resolution limits established by _refine_ls_d_res_high and
               _refine_ls_d_res_low.

                    sum|w[Y(obs)-Y(calc)]^2^|^1/2^
               wR = ------------------------------  +
                            sum|wY(obs)^2^|

                                  {sum~r~(w~r~|P(calc)-P(targ)|^2^)}^1/2^
                                + {--------------------------------}
                                  {     sum~r~(w~r~P(targ)^2^)     }

               Y(obs)  = the observed amplitude specified by
                         _refine_ls_structure_factor_coef,
               Y(calc) = the calculated amplitude specified by
                         _refine_ls_structure_factor_coef,
               w       = the least-squares weight,
               P(calc) = the calculated restraint values,
               P(targ) = the target restraint values,
               w~r~    = the restraint weight specified in
                         _refine_ls_restraints_weighting_scheme

               sum     is taken over the specified reflections
               sum~r~  is taken over the restraints
;

data_refine_ls_restraints_weighting_scheme
    _name                        '_refine_ls_restraints_weighting_scheme'
    _category                    refine
    _type                        char
    _definition
;              The weighting scheme applied to restraints in the least-squares
               process.
;

[Send comment to list secretary]
[Reply to list (subscribers only)]