This input block defines the information on the crystal, including unit cell parameters, space group symmetry, and reflection data (if needed).

        Note that the orthogonalization convention must have been defined before this block is input. In fact, it is good practice to define all the conventions at the very beginning of the program input.

        Remember that the following general input commands can also be used in this input block - comment, echo, and title.

        This defines the unit cell parameters of the crystal. The cell edges should be given in Angstroms, and the cell angles should be given in degrees.

        This terminates the input to this block, and the program will do the necessary calculations for this block. This include the calculation of reciprocal cell parameters, the orthogonalization matrix, and the definition of the space group rotation and translation matrices. In addition, the reflection data will be read in if they have been supplied.

        This defines the name of the file that holds the reflection data.

        This defines the format of the reflection file. Currently supported formats are-

• HKL - The reflection file that is output from the Scalepack program of the HKL package. The program will skip over the first 3 header lines of the file, so do not remove them yourself. The program will assume that intensity data is being input (see power command).


• CNS - The reflection file that is used for input to CNS. The file MUST have entries for both Fobs (labeled FOBS) and Sigma (labeled SIGMA) values for each reflection. The program will automatically set the POWER to 2.


• SHELX - The reflectin file that is used for input to SHELXL. The file will be read with format (3i4, 2f8.2), until a line with reflection index of 0, 0, 0 is reached.


• user-format - Specify a Fortran format statement here for the program to read a reflection file with a general format. For example, 3i4, 2f8.2.

        For the HKL, CNS, and SHELX formats, specifying the first letter of the format (H, C, and S) is enough for the program.

        This defines the rejection criteria for reflections. Reflections with F(input) < SIGCUT x Sigma(input), or with F(input) < FMIN, or with F(input) > FMAX (if a non-zero value has been supplied for FMAX) will be deleted. F(input) and Sigma(input) signify the values for F and Sigma as they are read in from the reflection file.

        This specifies whether reflection Amplitudes or Intensities are being input to the program. Specifying 'Input Amplitude' is the same as 'Power 2.0', whereas 'Input Intensity' is the same as 'Power 1.0'. See the POwer keyword below.

        This defines the lattice type of the unit cell. Supported types are P, A, B, C, F, I, and R. This command is not needed if the space group symmetry is specified with the space group symbol or number.

        This specifies whether observed phase information is available in the reflection file. The observed phase information is needed for the phased translation function.

        This specifies how the input structure factor values should be converted to reflection intensities. For example, if the reflection data file contains structure factors, POWER should be set to 2. If the reflection data files contains reflection intensities, POWER should be set to 1.

        This defines the resolution range within which the input reflection data will be saved. This resolution range should cover all the reflections that will be used later in RF, TF and SF calculations. The RF, TF and SF calculations will select reflections from those saved here.

        This specifies whether reflection amplitudes will be modified by a scale factor (OBSSCL) or a temperature factor (OBSBVL). If you want to increase the contribution of the high resolution terms ('sharpening'), give a negative B factor here. A positive B factor will decrease the contribution of the high resolution terms.

        This defines the symmetry of the space group, which can be done in three ways-

• Define the space group name, for example P212121. For monoclinic space groups, the regular space group names (P2, P21, C2) correspond to the b-unique setting. For c-unique settings, please use P2C, P21C, and B2 as the space group names. For rhombohedral space groups (R3 and R32), the hexagonal setting is assumed. For the rhombohedral setting, specify the space group as R3R or R32R.


• Define the space group number, for example 19.


• Define the space group symmetry operations, in the same format as in the International Tables, for example -x, 1/2+y, -z. The identity operation (x, y, z) does not need to be given. Centering of the space group should be given with the lattice command.

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