NLDFT Advanced PSD Report

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The NLDFT Advanced PSD report allows for more advanced computation of the pore size distribution of a material using two separate analyses and two non-local DFT models.

The NLDFT Advanced PSD report option provides the same calculations as the DFT Pore Size report option and more. The NLDFT report compares two sample files. The models that can be selected are restricted to only those models which have the same analysis temperature and analysis gas as the sample file that is open. For instance, if the sample file was analyzed with N2 at 77 degrees Kelvin, then only the N2 DFT models at 77 degrees Kelvin will be available in the Model drop-down list.

The model curve fit is shown in the lower right quadrant along with the adsorption isotherm. This curve fit is updated each time the calculation parameters change (selection of isotherm data points, choice of model, choice of regularization parameter).

A second sample file and second model is used to compute a more accurate pore size distribution (PSD), which is shown in the upper left quadrant. Typically, the second sample file will have used the same sample material as the first sample file yet will have used a different analysis gas and temperature.

In general, the isotherm for this second sample will be different than the first sample. The advanced DFT calculation takes the data from both sample files and combines all this data into a more accurate calculation of the pore size distribution. More accurate means getting the pore distribution at smaller pore sizes (a few Angstroms) as well as larger pore sizes (one thousand Angstroms).

  To make a successful advanced calculation, a second sample file must be selected using the Select button. A second model must also be selected. Use the options next to the two sample file names to select the isotherm data points for each sample. After selecting an option, the blue bars in the isotherm graph will be toggled to select either the red points or the green points. Once these selections have been done, the results will appear in the left-hand plots and a second isotherm will appear in the isotherm plot (lower right) as well as a second curve-fit. As the selection of points is adjusted, the DFT editor will recalculate the PSD results and also recalculate the two model curve fits.

NLDFT Advanced PSD Reports
Field or Button Description
Geometry
[drop‑down box]

Select the pore shape.

Model [drop‑down box]

Lists the models that meet the specified criteria and match the adsorbate and temperature of the sample data. If no models appear, no models meet the selected criteria. One model must be selected.

Regularization
[drop‑down box]

Select the extent of smoothing to apply to the data. If 0.20000 (user) is selected, enter a number in the text box giving a relative mass for the smoothing during deconvolution. Larger values produce more smoothing.

Select Reports
[group box]

Use to select the second sample file.

  For fields and buttons not listed in this table, see Common Fields and Buttons.

To run the NLDFT report:

  1. Go to File > Open. Select a sample file with a Complete status, then click Open.
  2. In the drop-down list at the bottom of the window, select NLDFT Advanced PSD. Graphs for the first sample file display and the sample description shows as the first group box title in the upper right corner of the window.

  1. Select the Geometry and Model from the drop-down lists for the first sample file.
  2. To select isotherm data points for calculation for the first sample file, ensure the option to the left of the first sample file description is selected. Slide the two blue bars on the isotherm graph to select data points. Without a second sample selected, the report will perform a single model DFT calculation and show the results in the two left-hand result windows.
  1. To calculate data from the second sample file, click Select to locate and open the second sample file with a Complete status. Graphs for the second sample file display and the sample description will display as the second group box title in the upper right corner of the window.
  1. Select the Geometry and Model from the drop-down lists for the second sample file.
  2. To select isotherm data points for calculation for the second sample file, ensure the option to the left of the second sample file description is selected. Slide the two blue bars on the isotherm graph to select data points. Data are automatically calculated for both sample files.
  3. Click Edit to make any necessary modifications to the second sample file.

 
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