Go to the $DLV_ROOT/structures/tutorials subdirectory and select MgO.str. The display will now appear as
Under the Edit menu select Model and Cut Slab (tutorial - Cutting a Slab).
Specify the Miller indices as 1 1 1 in the text box marked hkl and hit return. Two possible terminations will be displayed in the surface termination box. Select the first termination, number 0 (O Atoms), and then type 5 into the nlayers box and hit return. The structure panel will now display
The image can now be rotated and manipulated as desired. Under Display and Structure generate a number of repeat units (tutorial - Changing the number of Displayed Cells) and then rotate the image to produce the side view
Select a surface oxygen atom by clicking the left mouse button on it. Note that all the surface oxygens on both sides of the slab are highlighted as they are all related by symmetry. Cancel the selection by clicking in the background.
Under Edit select the Model menu and the Insert Atom option (tutorial - Inserting an Atom). Click on H in the scrolled list of atoms. Note that a line of H appears in the graphics window. Select a surface oxygen atom in the top layer of the slab and then select the Calculate from Selected Atoms option in the position section of the Insert Atoms panel. At first sight the H's have disappeared! This is not the case - they are simply hidden inside the oxygen atoms as currently they are centred on the same position in space. The z position displayed in the panel should be 2.431337
Replace this number by 3.43 and hit return. The H's will now appear above the O's.
Hit OK in the insert atom panel.We have now constructed a four layer polar slab of MgO(111) in which the Mg surface is terminated by an adsorbed OH group and the O surface is terminated by an adsorbed H atom. Note that this termination leads to a symmetric slab which is known to be very stable. This is the base model we will study using CRYSTAL. The resultant structure file is mgoh2o.str.
Saving an Image File
The image in the viewer can also be output in a variety of formats (JPEG, PBM and TIFF are currently supported). Under File select Save As and Image (tutorial - Saving Images). The following panel will now appear.
You can now define the properties of the image file and save an image of the displayed graphic.
Setting Up the SCF Calculation
Under Calculate select CRYSTAL and then SCF. The following panel will appear.
you are now in a position to set up the CRYSTAL job (see also - SCF Calculations).
Click on the Hamiltonian panel and then select the Density Functional radio box. Select B3LYP to set up the required Hamiltonian. This is sufficient for the default numerical DFT with CRYSTAL03, but with CRYSTAL98, under Auxillary Basis, select 12 s type functions which is the equivalent of the CRYSTAL command BASIS 3. Next select the Basis Sets panel and enter new basis sets for each atom. For H use the 5-11G* basis set, for O use the 8-51G basis and for Mg use the 8-511G set. Under SCF Convergence reset the linear Fock matrix mixing to 60%. Save the input file and compare the file you have generated with the input file mgoh2o.inp supplied.
Hit the Run button and execute CRYSTAL - note the exceutable should be available in your PATH environment variable. This takes about 19 minutes of CPU on a 180MHz SGI O2 R5000. The Job List panel will appear (see also - Listing Jobs) . Clicking on the job will display its current status. When the job completes click on Recover Files. This will load the wavefunction file into DLV for analysis and will extract preliminary information from the file for use in the Properties module. Whilst this occurs a second job entitled CRYSTAL Wavefunction will appear in the job list. When this completes, highlight this job and again, Recover Files. You can compare the output file with the on supplied as mgoh2o.out. To view the output file from your job select Show Logfile.
Calculating a Density of States
Select Calculate, CRYSTAL, Properties, Density of States (see also - Calculating Properties). The following panel will be displayed.
select the valence band region by pushing the Valence button. The Start Band will be reset to 14 and the End Band will be set to 25. To display a few unoccupied bands at the bottom of the conduction band change the End Band value to 30. Push the OK button to start the calculation. The Job List panel will again be displayed.
When the job completes select Recover Files. This causes the 1D Data Display panel to appear (see also - Displaying 1D Data). Select the Density of States and then select Draw 1D Data.
The above graphics will now be visible. To calculate the projected density of states close the 1D Data Display window by selecting OK. Return to Calculate, CRYSTAL, Properties, Density of States and select Atom Projection. Click on New Projection and then select the H atoms in the viewer window. The selected projection will appear. Select the Accept Projection button. Note this may be hidden at the bottom of the Projection window and you may need to use the scroll bar to reveal it. Run the job and recover the files. Slect the requested Density of States and the Draw 1D Data button. The total density of states and the density of states projected onto the H atoms will now be displayed.
Calculating a Band Structure
Now, close the 1D Data Display window and again select Calculate, CRYSTAL, Properties and select Band Structure. Select the Valence band.
again increase the End Band to 30. When the job completes, recover the file and display the band structure from within the 1D Data Display window.
Click on the graphic (to ensure it is selected) and then select Display, Graph. This enables you to edit the properties of the graph.
From the pull down menu titled Graph select Title. Click on the graph title and you can now enter a new descriptive title for the graphic. Note, the labels on the x-axis of a band structure plot are also entered as titles and can be edited in the same manner. The rescaling options for the X and Y Axes current available under the same pull down menu are the ones implemented by AVS. They are not well documented and are best left alone!
Printing a Graphic
To print your band structure, select File, Print. The following panel will now appear
Select the button marked ... on the right of the File text box.
You can now set a file name. Press OK to close the file browser and return to the print panel. Press Create Print File - the image has now printed to a postscript file.
Congratulations - you have now succesfully defined a structure, run CRYSTAL and analysed basic one dimensional properties.