scale set scale

maxhkl maximum hkl to be accepted for reflection selection

phi specify reflections to be phased

MEPHAS Option Code

mode of operation ms test 16 centric reflections

mo oscillate prior centric reflections¹

mc x step refl by x degr. 11<x<181 22.5

mf fit general reflections

maximum reflections nr n treat n reflections 16

maximum iterations it n iter per phase trial 1<n<36 13

convergence factor cv x stop when σ()*cv |-| 1.0

extend ms checking ex max 256 trials

entropy weight factor wt x used to select best phase set² 1.0

phi starting phases up use bdf phase values in phi line

reflection discard df x discard refl³ if Δ(F) < x 1.0

data set number ds n 1

print input reflections pr n print n lines of reflections 0

σ as fraction of si x used if σF is not on bdf 0.05

use xx1 prior map pi automatic for very large maps

use xx2 corr map ci automatic for very large maps

use xx3 rev Fourier ff automatic for very large maps

centric phase threshold th x min⁴ for phase to be centric 0.01

check correlation cr n n refl used to check corr of 0

min value of cf x min allowed in corr survey 0.1

pixel threshold ro x set pixels in input map 0.00001

non-MEDENS map nm med not prepared by MEDENS⁷

1 Requires phi input lines to specify reflections, and may not be run ab initio.

2 Criterion = wt*ENTROPY+( 1.0-wt)*CORRELATION. See option cr for causing correlation of unphased reflections to be calculated.

3 In cycling modes Δf=(-). In fitting mode Δf=*(-)

4 For values of cos or sin below this value the angle is set to nearest 0/90/180/270 value. Value must be between 0.00001 and 0.2

5 The n largest values will be selected up to a maximum of 1000. The cr option takes precedence if this value is set low.

6 Protects against zero and negative values in non-MEDENS maps.

7 Causes a preliminary scan of the med file to establish ln() and ln(). Uses the ro threshold to screen against holes.

scale 1 scale factor

2 scale group number

maxhkl 1-3 maximum |h|, |k|, |l| for automatic selection of reflections to be fitted and to protect for map resolution limitations

phi 1-3 h, k, l

4 φ in degrees

This field is optional. If left void the value used will be taken from the input bdf unless the up option has been used in the MEPHAS line. If the phase in the bdf is undetermined or the up option has been specified, the phase will be set to zero for general reflections, or to the lower value of the restricted centric phase as is appropriate.