Nicolet diffractometers produce a binary file containing intensity measurements. This file, in a form produced by the Data General/Nova Eclipse computer, may or may not need to be translated depending upon the machine on which XTAL is being run. The translated data is read from the NIC file. An existing archive bdf, prepared by STARTX, or some subsequent calculation (including a prior run of NICNAK), must be supplied. The data scan method is stored in logical record lrexpl:.

Each reflection record on the Nicolet file forms a packet in lrrefl: of the output bdf. Most items on the Nicolet file are transferred without modification. Three exceptions occur: first, h, k, and l are packed in the lrrefl: format; second, information about the standard reflections is separated from the reflection count and stored as separate entries; and third, the exposure time for the crystal is converted from hours to seconds. The option also exists to store the step counts or to discard them during the precessing.

The items present on the Nicolet file are as follows:

Nicolet lrrefl: NICNAK

Word ID number Mnemonic Description

1 1027 RFN reflection number, -ve is std.,

>32000 if φ spin for absorption

2 1 H Miller index h

3 1 K Miller index k

4 1 L Miller index l

5 1008 TTH 2θ at centre of peak

6 1007 OMG ω at centre of peak

7 1005 PHI φ at time of scan

8 1006 CHI χ at time of scan

9 1009 SCR scan range in degrees (may be 2θ or ω)

10 1017 SPD scan speed in degrees/min

11 1023 BGI counts at low angle background

12 1021 SCC scan counts

13 1024 BG2 counts at high angle background

14 1300 IRL relative intensity from Nicolet

15 1301 SIR Nicolet estimated std. deviation in I(rel)

16 1014 EXP exposure time in hours

17-112 1101-1196 CNT counts at each step position (96 steps)

The reflection number is complicated by being a signal as well as a count of the measurement. If RFN is negative, the measurement is that of a standard. If RFN is greater than 32000 or within selected range, the measurement is a "φ spin" standard used to establish absorption corrections. Analysis of this number is used to set the quantities RFN, reflection sequence number, and RFT, reflection type, in the output bdf. RFN becomes either the absolute value of the input RFN or the RFN less than the minimum φ-spin reflection number, as is appropriate. RFT becomes 0, 1, 2, or 3 corresponding to regular measurement, measurement of a standard, measurement of a φ spin standard, respectively, or background calculating reflection.

The program writes a packet which contains the items in the following list. The number of steps in the step scan data and the counts from the step scan are optional output.

lrrefl: lrrefl:

Word IDnumber Mnemonic Description

1 1 HKL packed HKL

2 1005 PHI φ during scan

3 1006 CHI χ during scan

4 1007 OMG ω at reflection centre

5 1008 TTH 2θ at reflection centre

6 1009/1010 SCR 2θ or ω scan range

7 1014 EXP exposure time in seconds

9 1017 SPD scan speed in degrees/min

10 1021 SCC scan counts

11 1023 BG1 counts at low angle background

12 1024 BG2 counts at high angle background

13 1027 RFN reflection sequence number

14 1300 IRL relative intensity

15 1301 SIR sigma of relative intensity

16 1100 STP number of steps in step scan

17-112 1101-1196 CNT counts at each of STP steps

Reads cell and symmetry data from input archive bdf

Writes reflection data to the output archive bdf

Reads Nicolet binary file from file nic

NICNAK t2t steps 96

In this example the scan method of the data collection was θ-2θ and 96 steps were used.