Input Data

The minimal information required by Quanto includes:

· Diffraction pattern

· List of phases in the mixture

· Wavelength

· Type of radiation (if Synchrotron or constant wavelength neutron have been used; X-Ray home source is the     default)

· Information on the instrument (monochromator and geometry; Bragg-Brentano in reflection mode is the default)

 

These information can be supplied by the graphical interface or by an input file with default extension .qua. The input files for cpd1a and cpd2 samples of R.R. on QPA  are distributed with the program and are shown below:

cpd1a.qua

%window

%mixtures cpd1a

%init

%job cpd1-a, CPD Round Robin mixture

%data

Phase D:\Quanto\bank\ corundum.pha

Phase D:\Quanto\bank\ zincite.pha

Phase D:\Quanto\bank\ fluorite.pha

Pattern D:\Quanto\data\cpd-2.dbw

Range 5.0 150.0 0.02

Record 8

Filetype 2

Wavelength 1.54056 1.54433 0.5

Polcorrection 1

Polfraction 0.8

%continue

 

cpd2.qua

%window

%mixtures cpd2

%init

%job cpd2, CPD R. R. mixture, OP along 001 for brucite

%data

Phase D:\Quanto\bank\corundum.pha

Phase D:\Quanto\bank\zincite.pha

Phase D:\Quanto\bank\fluorite.pha

Phase D:\Quanto\bank\brucite.pha

Parameter D:\Quanto\data\brucite.par

Pattern D:\Quanto\data\cpd-2.dbw

Range 5.0 150.0 0.02

Record 8

Filetype 2

Wavelength 1.54056 1.54433 0.5

Polcorrection 1

Polfraction 0.8

%continue

 

The input file consists of a sequence of commands and directives; the commands are headed by the ‘%’ character and directives must follow the related command.

The list of allowed commands follow:

%window                 Graphic window is required

%nowindow             Graphic window is not required

%init                         initialize the direct access file

%mixture string        to specify the name of the mixture to investigate. The program creates a direct access file named string.bin to store data                                   and results.

%job string              a caption is printed in the output file

%data                      to supply all the necessary input data

%prelim                    to run the Preliminary Procedure

%rietveld                  to run the Rietveld Procedure

%end                        indicates the end of the input file

%continue                 if specified after data directives, the commands prelim, rietveld and end are automatically carried out.

 

All commands and directives are in free format and case independent. If the first non-blank character is ">", then the record is interpreted as a comment.

 

Data directives

Pattern filename

Filename is the name of profile counts file (up to 256 character).

 

Phase filename

Filename is the name of .pha file containing structural information to be read from the Quanto Data Bank.

 

Range thmin thmax thstep

Thmin, thmax and thstep are the minimum , the maximum and the step, respectively, of the powder pattern (thmin must be equal to the value corresponding to the first count in the pattern file).

 

Thlow thmin

Thmin is the value (not corresponding to the first count in the pattern file) to be used as the minimum value for the powder pattern.

 

Wavelength w1 w2 R2/1

If a monochromatic radiation has been used to collect the experimental pattern, w1 is its value (in Angstrom).

If a doublet 1 / 2 has been used to collect the experimental pattern, w1 is the value, w2 is the value, R2/1 is the intensity ratio.

 

Polcorrection n

n = 0 : a crystal monochromator has not been used for data collection

n = 1 : a crystal monochromator on incident beam has been used for data collection

n = 2 : a crystal monochromator on diffracted beam has been used for data collection

 

Polfraction x

x = cos M , M being the Bragg angle of the crystal monochromator

 

Record n

n is the number of counts per record (max value is 10).

 

Filetype n

This directive allows to manage different type of powder pattern, with different content; the format of data is not required (free format is used):

n = 1 : values and counts are stored into the pattern file as alternating columns

n = 2 : only counts are stored into the pattern file

n = 3 : a raw of values and a raw of counts are stored into the pattern file

 

Jump

This directive must be used when the first line of the powder pattern file is a comment.

 

Format string

String is the format to read counts from the pattern file.

 

Neutro

This directive must be used when a constant wavelength neutron radiation has been used.

 

Synchrotron

This directive must be used when a synchrotron radiation has been used.

 

Noanomalous

This directive is used not to take anomalous scattering into account for structure factors calculation.

 

Outfile

This directive allows to read the anomalous scattering factors (f’ and f’’) and the mass absorption coefficients of each atomic specie from an external file named "scafact.dat"; this file must be prepared by the user when powder data have been collected with a wavelength different from Cu- and Mo- .

 

Interpolation

To use the linear interpolation points for the default background model.

 

Chebyshev

To use the Chebyshev approximation for the default background model.

 

Debye x

This directive allows to specify that the powder data have been collected by using a Debye-Scherrer geometry instrument; x = R, is the linear absorption sample coefficient, R is the capillary radius (in mm).

 

BBtrasmission x

This directive allows to specify that the powder data have been collected by using a Bragg-Brentano diffractometer in trasmission mode; x = t, is the linear absorption sample coefficient, t is the effective sample tickness (in mm).

 

Parameter filename

This directive allows to associate to each phase a parameter file containing phase dependent information . The information is supplied by means of suitable directives (see "Parameters file directives" section). Filename must be the same of the .pha file, the default extension is .par.

 

Reflection filename n1 n2 n3

This directive allows to associate an external intensity reflections file to each phase. These intensities will be used instead of those calculated by the model. Filename must be the same of the .pha file, the default extension is .hkl. This kind of file must include, for each reflection and in the specified order: Miller indices, |Fo| or |Fo|2 value and, eventually, (|Fo|) or (|Fo|2); the first line of the file must indicate the format to read the information, otherwise a free format is used.

n1 = 1     |Fo| are supplied, 

n1 = 2     |Fo|2 are supplied

n2 = 0    (|Fo|) or (|Fo|2) are not supplied, 

n2 = 1     (|Fo|) or (|Fo|2) are supplied

n3 = number of reflections per record

 

Standard filename w

This directive allows to specify the phase added as standard. Filename is the corresponding .pha file and w is the known weight fraction (x100) added to the original mixture.

 

Zero x

This directive allows to supply a starting value of the instrumental zero-shift. The correction x is applied to the measured angular positions according to    ' = i -  x/2

 

Parameters file directives

 

Orpr h k l  G

This directive allows to supply a preferred orientation direction for the corresponding phase.

h k l are the Miller indices of the plane and G is the March-Dollase factor.

 

Orp2 h k l   G   f2

This directive allows to supply a second preferred orientation direction for the corresponding phase. h k l are the Miller indices of the plane, G is the March-Dollase factor and f2 is the fraction ( 1.0 < f2 > 0.0). G and f2 are refinable parameters. Accordingly, the fraction of the first plane f1 = 1.0 - f2.

 

Orp3 h k l   G   f3

This directive allows to supply a third preferred orientation direction for the corresponding phase. h k l are the Miller indices of the plane, G is the March-Dollase factor and f3 is the fraction ( 1.0 < f3 > 0.0). G and f3 are refinable parameters. Accordingly, the fraction of the first plane f1 = 1.0 – (f2 + f3).

 

Radius x

This directive allows to supply the average particle size of the corresponding phase to apply the Brindley microabsorption correction. x is the radius of the particles in micron.

 

Shape string

This directive allows to choice the function to model the profile shape of peaks. String can be:

Pearson (the default), Pvoigt (Pseudo-Voigt), Gaussian and Lorentzian.

 

Fwhm w v u

This directive allows to supply the values of the Full Width at Half Maximum w, v and u parameters for the corresponding phase. w, v and u are defined by the Caglioti formula and are refinable parameters.

 

Mixpar  m 0   m 1   m 2

This directive allows to supply the values of the mixing  m 0 ,  m 1 and   m 2 parameters for the corresponding phase, when Pearson VII or Pseudo-Voigt profile shape function have been selected. m 0 ,  m 1 and   m 2 are refinable parameters.

 

Asymmetry x

This directive allows to supply the value x of the asymmetry parameter for the corresponding phase. x is a refinable parameter.

 

Fwmin x

This directive allows to supply the minimum value of the Full Width at Half Maximum for the corresponding phase. This value will be used as a threshold in the least squares refinement. The default value is 0.001 degrees.

 

Fwmax x

This directive allows to supply the maximum value of the Full Width at Half Maximum for the corresponding phase. This value will be used as a threshold in the least squares refinement. The default value is 2.0 degrees.

 

Mixmin x

This directive allows to supply the minimum value of the Pearson VII or Pseudo-Voigt mixing parameter for the corresponding phase. This value will be used as a threshold in the least squares refinement. The default value is 0.95.

 

Mixmax x

This directive allows to supply the maximum value of the Pearson VII or Pseudo-Voigt mixing parameter for the corresponding phase. This value will be used as a threshold in the least squares refinement. The default value is 20.0.

 

arange (or brange or crange or alrange or berange or garange) x

This directive allows to supply the maximum absolute percentage variation x of the specified cell parameter (a, b, c, alfa, beta, gamma) to be used in the least squares refinement. After each l.s.q. cycle, the new cell parameter is compared to the previous value (1) and to the starting value (2).

A cell parameter variation > x is refused for case (1)

A cell parameter variation > x /2 is refused for case (1) for phases with wi < 10.0%

A cell parameter variation > 2x is refused for case (2)

The default value is x = 10%.

 

Lebail

This directive allows to apply the extraction intensities Le Bail algorithm for the corresponding phase. The starting intensity values are calculated by the model (or a random atom) supplied with the .pha file.

 

Rietveld directives

 

Noautomatic

This directive allows to enable the automatic Rietveld refinement Procedure. A user strategy can be supplied by graphics.

 

Epsconver

This directive allows to supply the value to be used as a convergence criterium in the least squares refinement. The default value is 0.3.

 

Weight n

This directive allows to select the weighting scheme to adopt in the least squares refinement

( å [ wi yo(i) – yc(i)]2 = min) .

n = 1, wi = 1.0

n = 2, wi = 1.0/ yo(i)

n = 3, wi = 1.0/ [yo(i)]2

The default value is n = 2.