(Balsac/Lattice sessions only) Balsac offers a rather powerful tool to build nanotubes from one or a set of adjacent netplanes of single crystals in the most general way. Various options are available to modify the size (radius, length) of the tube as well as its visual appearance and will be discussed in detail in the following subsections.
opens the tube builder window which looks different depending on whether or not a tube has been defined previously.
(A) Without a tube definition the tube builder window shows as
This window contains three buttons at the bottom.
L-clicking the “Tube” button with no tube definition will set the default definition of a (6, 0) tube of height Ht = 1 (in units of the atom coordinates).
L-clicking the “Hide/close” button closes the tube builder window and redraws the lattice section in the graphics window.
The “Visualize” button is disabled when there is no tube definition.
(B) With a tube defined previously the tube builder window shows as
This window contains three parts,
· the title part gives a shorthand notation of the nanotube parameters in a title line reading
(n, m) tube, N3 layer(s), length =Len
which indicates that N3 layers of a lattice section (N3 being defined inside the lattice builder window) are used to construct a nanotube where the rolling vector is given by the linear combination Rr = n R1’ + m R2’ of the two vectors R1’, R2’ describing the periodicity of the chosen (hkl) netplane. Further, the title line includes the length Len of the rolled nanotube which may be changed below.
· the tube definition part in the middle of the window shows details of the present tube definition and allows further changes. The two boxes next to “Tube indices” show the present values of the (integer valued) mixing components n, m of the rolling vector Rr where both values can be changed by typing inside the input boxes. The next two lines below “Rolling vector” define vector Rr in its Cartesian coordinates as
(x, y, z) = (xr, yr, zr)
together with its length as
Length = LenRr
Then the symmetry properties of the nanotube are shown by either
Translational symmetry, periodicity length = LenPer
if the tube can be characterized by a periodic arrangement of cylindrical unit cells whose length along the tube axis is given by LenPer, followed by a line
R(n’, m’) = (xt, yt, zt)
which shows the axial vector Rt, by mixing components n’, m’, analogous to those of Rr, and by its Cartesian coordinates. This lattice vector of the netplane is perpendicular to Rr and defines the netplane periodicity perpendicular to the rolling direction of the tube. If the netplane is rolled to form the nanotube vector Rt points along the tube axis.
If the tube shows only screw symmetry elements along its axis by no translational symmetry.
This is followed by the definition of the tube length confining the nanotube along its axis. The input box next to “Tube length: abs. =” show the present value of the absolute length Lt (in units of the atom coordinates) where the value can be changed by typing inside the input box.
There is second input box next to “rel. =” which shows the relative length ht of the tube given by a multiple of
o the periodicity length defined by ht = Lt / LenPer if the nanotube has translational symmetry,
o the tube diameter (= 2 x tube radius) if the nanotube has only screw symmetry.
where the value of the factor ht can be changed by typing inside the box.
Finally, the radius of the nanotube, defined by Radr = LenRr / (2π) and the number nc of elementary cells of the netplane forming the nanotube section are shown in one line by
Tube radius = Radr , nc primtv. cells
· the action part at the bottom of the window shows a frame “Display” containing two radio buttons, entitled “Planar” and “Cylinder”, which determine the type of graphics representation used in the visualization of the nanotube, see below. The present setting is indicated by a black dot filling one of the two buttons and can be reset by L-clicking the corresponding radio button.
· “Clear” removes the present tube definition, erasing all parameters inside the tube builder window (showing the tube builder window without a tube definition, see (A) above), and recovers the previous bulk section. Further, the “Clear” button will be replaced by the “Tube” button inside the tube builder window without a tube definition. The reset has to be confirmed in a message box reading
Remove present tube definition ?
L-clicking “Yes” inside the message box removes the tube
definition while L-clicking “No” returns to the tube builder
window without any further action.
Note that the previous bulk section will show in the graphics window only after L-clicking the “Visualize” button, see above.
· “Visualize” button saves the present tube settings, rebuilds the (updated) nanotube section, and redraws it in the graphics window according to the representation type defined by the display buttons. If button
- “Cylinder” was selected, the nanotube section will be shown in its natural appearance as a cylindrical tube.
- “Planar” was selected, all atoms of the nanotube section will be shown in a planar lattice reflecting the netplane section chosen to form the nanotube which corresponds to “unrolling” the tube section.
After the drawing the tube builder window is left open for further changes.
· “Hide/close” button closes the tube builder window and redraws the nanotube or lattice section in the graphics window. All present tube parameters will be saved before closing the window.
Note that the use of the tube builder requires basic knowledge of bulk/surface crystallography.