Selection of basis sets for atoms    
        and molecules in cavities          
                                        
       F. Rajadell, J. Planelles,             
    W. Jaskolski, and C. Zicovich-Wilson  
                                       
                                       
                Abstract  

A method of selection of  basis functions for the
quantum-chemical description of atoms and molecules inside spherical
and cuboidal cavities is presented. The method consists of two
independent  steps. First, the appropriate GTO or STO
exponents are chosen by fitting the basis functions to 
cutoff orbitals. The criterion of  maximal orbital density
inside the cavity is next applied to form the final model
orbital space. The method presents the fundamental advantage over many
other methods of being trivially applicable in standard quantum 
chemical progam packages. As an illustration, the method is applied to the
hydrogen atom in a spherical box. The use of contracted basis
functions is also discussed.