## 6.2.4. SECTION OPTION, [S]

next, previous Section / Table of Contents / Index [S] This option allows you to choose the size of a lattice section. If BALSAC/LATTICE is started from scratch in an interactive session (without a structure input file) this option shows an explanatory text ========== SECTION OPTIONS ======================================== Select the size of a rectangular lattice block to be displayed. The block is defined by layers of N1 x N2 atoms where N3 layers are stacked. NINIT sets the index of the initial plane ( bottom of block ) for non-primitive lattices ( NINIT = 1 for primitive lattices ). Section N1,N2,N3,NINIT : =================================================================== asking for four integers n1, n2, n3, ninit describing the section size and initial layer. In BALSAC lattice sections contain all atoms within a rectangular block with a base area of length n1*|R1'| and width n2*|R2'|*sin(R2',R2') and a height corresponding to n3 layers. Here (R1', R2', R3') stands for the (hkl) surface adapted lattice vector set, see Sec. 5.1. (For additional spherical constraints see below.) The stacking direction of the lattice planes is along the normal vector defined by Miller indices, see Sec. 6.2.3. Further, the index ninit gives the number of the starting layer used in the stacking procedure. This is useful only for non-primitive lattices where neq > 1 inequivalent surface termination planes exist and where different ninit values can be used to show the different terminations. Note that ninit will always be taken modulo neq (see lattice plane option output). After correct input BALSAC moves to the view option, see Sec. 6.2.6. Selecting [S] from the main option menu of BALSAC/LATTICE shows the section menu S ========== SECTION OPTIONS ======================================== [B]lock : N1,N2,N3= n1 n2 n3 Lx,Ly,Lz= lx ly lz [I]nitl : NINIT(1 - neq)= ninit [S]phere: (X,Y,Z)= ( xsph ysph zsph ) Rmin,Rmax= rmin rmax [X]plot [?,]esc ============================================================= 60 == where n1, n2, n3 give the present lattice section size in multiples of (projected) lattice vectors, see above, and lx, ly, lz are the actual lengths of the rectangular block. The second line of the menu, starting with "[S]phere: ...", shows only for non-primitive lattices if neq > 1 translationally inequivalent lattice planes exist. Here ninit defines the number of the lattice plane used as the starting layer in the stacking procedure. Respective net plane numbers can be obtained from the net plane adapted lattice listing of the text analysis option (option [M] of the text analysis menu), see Sec. 6.2.14. The third line of the menu, starting with "[S]phere: ...", and the following line indicate an additional spherical shell constraint which influences the shape of the lattice section. Here (xsph, ysph, zsph) defines the center (in absolute cartesian coordinates) of a spherical shell with inner/outer radius rmin/rmax and only atoms of the rectangular lattice block which are inside the shell will be considered for the lattice section, see below. If no spherical shell constraint is defined the above lines will be replaced by [S]phere: undefined Note that an existing spherical shell constraint is also indicated in the BALSAC/LATTICE main option menu by a line sph = xsph ysph zsph rmin rmax after the line starting with "[S]ection ...", see Sec. 6.2.0. > [B] selected from submenu S allows you to change the size of the rectangular lattice section. In BALSAC lattice sections contain all atoms within a rectangular block with a base area of length n1*|R1'| and width n2*|R2'|*sin(R2',R2') and a height corresponding to n3 layers. Here (R1', R2', R3') stands for the (hkl) surface adapted lattice vector set, see Sec. 5.1. The prompt Block size N1,N2,N3 ( n1old n2old n3old ) : asks for three integers n1, n2, n3 determining the section size where the previously defined values are shown as n1old, n2old, n3old. After meaningful input BALSAC returns to submenu S. If the section size (number of atoms) defined by N = n1*n2*n3 exceeds the internal maximum namax (=2001 for DOS, =8000 for Unix systems) no warning will be given at this point. However, a warning WARNING: No. of atoms ( N ) exceeds internal maximum ( namax ) Plot will be incomplete will be issued whenever plotting/listing of the lattice section is initiated and the plot may be truncated. The warning can be ignored if layer-by-layer display mode is used and n1*n2 < nmax or if a spherical shell constrained restricts the total number of section atoms below nmax. > [I] can be selected from submenu S only for non-primitive lattices if neq > 1 translationally inequivalent lattice planes exist. Here the option allows you to redefine the number ninit of the lattice plane used as the starting layer in the stacking procedure. This is particularly useful if different surface termination planes of non-primitive lattices are to be displayed. The prompt Initial plane NINIT ( initold / 1 - neq) : asks for a new lattice plane number 1<= init <= neq where initold is the previously defined value. Respective net plane numbers can be obtained from the net plane adapted lattice listing of the text analysis option (option [M] of the text analysis menu), see Sec. 6.2.14. After meaningful input BALSAC returns to submenu S. > [S] selected from submenu S allows you to define, redefine, or remove a spherical shell constraint to modify the shape of a lattice section. Here (xsph, ysph, zsph) is the center of a spherical shell with inner/outer radius rmin/rmax and only atoms of the rectangular lattice block which are inside the shell will be considered for the lattice section. If no spherical shell constraint is defined the prompt Sphere NC,X,Y,Z, RMIN,RMAX ("-1,5*0"=esc) : asks for six numbers defining the constraint where the first four numbers refer to the shell center given either in absolute cartesian coordinates (0,xsph,ysph,zsph) or denoting the center of an existing atom na by (na,0,0,0). The last two numbers set the inner and outer radius, rmin and rmax, of the shell. After meaningful input BALSAC returns to submenu S. Dummy input "-1,5*0" returns to submenu S without a shell definition. If a spherical shell constraint is already defined as indicated in menu S above the shell constraint menu SS shows as ============================================================== [A]ll [C]enter [R]adii [E]rase a[N]alyze [D]ispla [?,]esc ======================================================== 61 == allowing you to redefine or remove the constraint. > > [A] selected from submenu SS defines a new constraint from scratch overriding any previous definition. (This option is identical to that used for the initial constraint definition explained above.) The prompt Sphere NC,X,Y,Z, RMIN,RMAX ("-1,5*0"=esc) : asks for six numbers where the first four numbers refer to the shell center given either in absolute cartesian coordinates (0,xsph,ysph,zsph) or denoting the center of an existing atom na by (na,0,0,0). The last two numbers set the inner and outer radii, rmin and rmax, of the shell. After meaningful input BALSAC returns to submenu S. Dummy input "-1,5*0" returns to submenu S with the previous shell definition left unchanged. > > [C] selected from submenu SS redefines the shell center of an existing constraint. The prompt Sphere center NC,X,Y,Z ("-1,3*0"=esc) : asks for four numbers defining the new shell center given either in absolute cartesian coordinates (0,xsph,ysph,zsph) or denoting the center of an existing atom na by (na,0,0,0). After meaningful input BALSAC returns to submenu S. Dummy input "-1,3*0" returns to submenu S with the previous shell definition left unchanged. > > [R] selected from submenu SS redefines the inner and outer shell radii of an existing constraint. The prompt Min/max radii RMIN,RMAX ("0,0"=esc) : asks for two numbers defining the new inner and outer radii, rmin and rmax, of the shell with rmax > rmin > 0. After meaningful input BALSAC returns to submenu S. Dummy input "0,0" returns to submenu S with the previous shell definition left unchanged. > > [E] selected from submenu SS erases an existing constraint and BALSAC returns to submenu S. The missing constraint will be indicated by a line "[S]phere: undefined" in submenu S, see above. > > [N] selected from submenu SS analyzes an existing constraint and shows the result by Boundary analysis : antext Xrange: sphere ( xmin , xmax) block ( lxmin , lxmax ) Yrange: ( ymin , ymax) ( lymin , lymax ) Zrange: ( zmin , zmax ) ( lzmin , lzmax ) ** Press [C], L-click to continue ** where the cartesian intervals (xmin, xmax), (ymin, ymax), (zmin, zmax) give the cube enclosing the spherical shell and (lxmin, lxmax), (lymin, lymax), (lzmin, lzmax) describe the coordinate range of the rectangular block. The analysis text antext reads Sphere inside block if the spherical shell lies inside the rectangular lattice block leading to an overall spherically shaped lattice section or Sphere (partly) outside block if the spherical shell intersects the surface of the rectangular lattice block leading to a spherical lattice section with planar pieces cut off. Note that if the shell lies completely outside the rectangular block no atoms will be generated. This can be checked by comparing the cartesian intervals shown above. After the analysis output BALSAC returns to submenu S. > > [D] selected from submenu SS shows up to 10 lines of the most recent output generated by the graphic analysis option, see Sec. 6.2.14.2, by ============ Latest Graphics Output ================== 1: Xyz,R,Id( n1)= x y z rad nuc ... ====================================================== after which BALSAC returns to submenu SS. This allows you to look up and use numerical output from the analysis for input within submenu SS. > > [,] selected from submenu SS returns to the section menu S. > [X] selected from submenu S plots the lattice section (switching to graphics mode (DOS) or opening a graphics window (Unix)) or lists its atom coordinates depending on the plot/list mode defined in the graphics option, see Sec. 6.2.7. > [,] selected from submenu S returns to the BALSAC/LATTICE main option menu, see Sec. 6.2.0. next, previous Section / Table of Contents / Index