Unique Input Statements

Unique Input Statements

ACCEPT FO-FC <Upper limit>
ACCEPT FO    <Lower limit> <Upper limit>
ACCEPT FC    <Lower limit> <Upper limit>

This statement allows the user to specify particular limits to the acceptable values for the diffraction data. It permits limits to be placed on the value of FO, FC, and FO-FC. These limits are specified in the units of the diffraction data after scaling. Therefore all data is used to determined the scale factors.

FC  <File name> [FORMAT {HKL | PACKED | MAP}]

This statement gives the name of the file which is the source of the calculated structure factors. If a map file is given the calculated structure factors are arrived at by inverting the map. If no FC statement is given the Fc's will be calculated from the coordinates of the model.

FILE <File Id> <File name> [FORMAT (HKL | MAP | PACKED)] -
                           [SCALE <Value>] [BLUR <Value>]

This command describes an external binary data file to the program. This file is subsequently referred to by the arbitrary ``File Id''. If the file's format is not HKL, which is the default, the type of file may be given via the FORMAT option. When the data are read from the file a scale factor and blur may be applied. Because of the extreme difficulty of applying a blur to an electron density map, when the file is a map file, the BLUR option is presumed to indicate that the map has a already been blurred by the indicated amount.

In Rfactor this statement is only useful when using the AGARWAL and NORMAL_MATRIX commands.

FO  <File name> [FORMAT {HKL | PACKED | MAP}]

This statement gives the name of the file which is the source of the observed structure factors. If a map file is given the observed structure factors are arrived at by inverting the map. If no FO statement is given the Fo's will be calculated from the coordinates of the model. (I know this sounds a little weird, to define the structure factors calculated from a model to be Fo's. However sometimes it is useful to compare two calculated data sets, such as when someone wishes to determine just how different two models are.)

SET [K <Value>] [B <Value>] [KSOL <Value>] [BSOL <Value>]
    [B11 <Value>] [B22 <Value>] [B33 <Value>]
    [B13 <Value>] [B13 <Value>] [B23 <Value>]

This statement allows the user to set the value of any of the scaling function parameters. Any parameters which are not explicitly set are calculated by Rfactor by minimizing the squared difference between the two data sets. A SET statement clears all information about previous SET statements and resets any scale factors which have already been determined.

If any anisotropic scale factor component is set to zero they all are. If is set to zero is as well.

If the SIGMA option is set, any unspecified parameters are fit with each reflection weighted by .

SIM [<A> <B>]

This statement causes Sim weighting to be applied to any difference coefficients later produced with the PUNCH command. This statement would be used whenever a Sim weighted map is desired. The two parameters are optional. If they are given (As with all programs in this package typing 0.0 is different than typing nothing at all. 0.0 is accepted as a zero, not as an indication that the default is desired.) they specify a single Gaussian fit to the r.m.s. difference coefficients. If they are not given on the statement the program will calculate the best values for A and B and apply them to the data.

If the SIGMA option is set the data used to determine A and B are weighted by .

WEIGHT [RFACTOR <Value>] [ROTATION <Value>]
WEIGHT [PHASE <Value>]   [REALSPACE <Value>]

This statement allows the user to specify a weighting factor that will be applied to the function value, gradient, and curvature written out by the FUNCTION, GRADIENT, and CURVATURE commands. If a weight for the current module is not given a weight of 1.0 is assumed. During the short loops the same weight must also be applied. To ensure that this will occur you should keep the WEIGHT statement in your TNT control file.. If a weight for another restraint (such as BOND, or ANGLE) is given to this program on a WEIGHT statement the additional weights will be ignored.