Daniel,
 
Try giving non-zero values for the ISOERROR.
 
If that doesn't work, post your Se site coordinates, space group and unit cell parameters.
 
This may also be a special case with P1, in that the origin can be anywhere.  Try fixing one of your atoms to a specific coordinate (don't refine it), and fit the rest.
 
Good luck-
 
Steve
 
-----Original Message-----
From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Daniel Adams
Sent: Friday, January 19, 2007 11:36 AM
To: [log in to unmask]
Subject: mlphare for SAD data

Hi everyone
I am trying to refine Se sites  (obtained by SHELXD) using Mlphare programme. The dataset is SAD dataset, space group is P1. When I try to refine 'xyz and alternate OCC and B values' with following script:

title [No title given]
labin  FP=F SIGFP=SIGF
   FPH1=F SIGFPH1=SIGF
   DPH1=DANO SIGDPH1=SIGDANO
labout -
    ALLIN -
    PHIB = PHIB_mlphare1 -
    FOM = FOM_mlphare1 -
    FH1 = F_aps_mlphare1 -
    PHIH1 = PHI_F_aps_mlphare1 -
    FHA1 = DANO_aps_mlphare1 -
    PHIHA1 = PHI_DANO_aps_mlphare1
fhout deriv -
    1
apply
cycle 10
skip 100
resolution 15.0 2.8
print AVE AVF
deriv Se
dcycle -
    phase all -
    refcyc all -
    kbov all
ISOERROR 0.00 0.00 0.00 0.00 -
    0.00 0.00 0.00 0.00
ANOERROR 25.75 30.10 16.83 21.78 -
    15.89 23.29 26.93 29.55


The programme fails and shows following error:


**** IN SUBROUTINE MATSOL: DET IS LESS THAN 10E-30****
 **** Possible causes: *****
 You have an atom on a special position where one parameter must be fixed?;
 You have not fixed one  coordinate  in a polar spacegroup? eg: one XYZ in P1, one Y in P21; one Z in P3
 You are refining a property whch is indeterminate?
  eg: AX or AOCC without setting DPH; AX when AOCC equals zero

Is there something I am doing wrong in input file or I should  fix these parameters ? If yes how ?

Thanks in advance

Cheers

Daniel 

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