On May 3, 2011, at 19:07 , Amin Torabi wrote: > the Atomic-Position input card, which is mandatory, specifies > the type and coordinates of each atom in the unit cell. Then, > my question is why we need to specify the number of atoms, > number of type of atoms and even celldm in the system input card?
celldm specifies the unit cell: a piece of information that is not contained in atomic_positions card. The number of atoms and the number of species could in principle be deduced from the contents of the atomic_positions card. This would however require a sizable amount of programming and introduce a number of undesirable complications into the code. There is a compromise to be struck between ease of use by ordinary users and ease of maintainance by developers. P. --- Paolo Giannozzi, Dept of Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
