3.6. SWITCHING BETWEEN BALSAC/LATTICE AND BALSAC/CLUSTER SESSIONS

next, previous Section / Table of Contents / Index LATTICE sessions always deal with periodic arrangements of atoms and any modification is subject to this periodicity constraint. On the other hand, CLUSTER sessions deal with non-periodic arrangements of atoms (molecules, clusters) where single atoms can be manipulated. BALSAC offers structure transfer - from a LATTICE to a CLUSTER session where a finite section of a periodic lattice is converted to a finite atom cluster without periodicity, - from a CLUSTER to a LATTICE session where a molecule is converted to an elementary cell of a periodic lattice. These transfer options allow you to modify structures differently depending on which session you are running in. For example, you can create a periodic crystal surface in a LATTICE session, transfer its structure to a CLUSTER session, and add additional single adsorbate molecules or non-periodic perturbations. On the other hand, you can build a molecule in a CLUSTER session, transfer its structure to a LATTICE session, and create a rather complex molecular crystal. Note, however, that a transfer from a LATTICE to a CLUSTER session always destroys the periodicity information of the lattice while all atom coordinates and graphics parameters are conserved. Switching between LATTICE and CLUSTER sessions of BALSAC is possible at any time using the transfer options of the main option menus or direct transfer in graphics mode. If you select [U] from the BALSAC/LATTICE main option menu you get a prompt Confirm transfer: [S]tructure->CLUSTER CL[U]STER from scratch [?,]esc where selecting [U] moves to the startup menu of a CLUSTER session to start a new structure from scratch or to load an appropriate structure file. If you select [S] in the above menu the coordinates of all atoms created in the LATTICE session together with graphics data are written on a transfer file 'balsac.trp' in PLOT3D format and used immediately as input for a CLUSTER session. Note that if you used layer-by-layer display of your lattice section in a LATTICE session then you can transfer only the atoms of the layer you displayed last. You have to build the complete lattice section in atom-by-atom mode in a LATTICE session to guarantee that all atoms are transferred correctly. If you select [L] from the BALSAC/CLUSTER main option menu you get a prompt Confirm transfer: [S]tructure->LATTICE [L]ATTICE from scratch [?,]esc where selecting [L] moves to the startup menu of a LATTICE session to start a new structure from scratch or to load an appropriate structure file. If you select [S] in the above menu the coordinates of all atoms created in the CLUSTER session together with graphics data are written on a transfer file 'balsac.trl' in LATUSE format and used immediately as input for a LATTICE session. Here the atoms of the CLUSTER session are interpreted as forming the crystallographic elementary cell of an orthorhombic lattice (which you may modify later inside the LATTICE session), see Sec. 6.3.10. As an example, try to build an fcc crystal of C60 "Buckey balls" as elementary units. Note that all structure and graphics data of a session where you transfer from are saved in a backup file (LATUSE formatted 'balsac.svl' in a LATTICE session, PLOT3D formatted 'balsac.svc' in a CLUSTER session) before transfer takes place. So you can always return to the previous session without loss. next, previous Section / Table of Contents / Index