[molpro-user] [Molpro-user] Segmentation fault with FCI

Peter Knowles KnowlesPJ at Cardiff.ac.uk
Fri Oct 3 15:20:56 BST 2008

On 2 Oct 2008, at 14:30, Lorenzo Lodi wrote:

> To estimate the RAM requirement of a FCI calculation with molpro is it
> preferable to use the Weil formula (which refers to the number of
> spin-adapted configurations) or just binomial(2k,n), because Slater
> determinants are used? And how does symmetry reduce the memory  
> requirements?

Neither. The code uses all Slater determinants of a particular M_S and  
a particular point group irreducible representation. Thus without  
symmetry the number is binom(m,N/2+M_S) * binom(m,N/2-M_S) for N  
electrons in m orbitals . With symmetry there is no simple exact  
formula, but just divide the no-symmetry number by the order of the  


Prof. Peter J. Knowles
School of Chemistry, Cardiff University, Main Building, Park Place,  
Cardiff CF10 3AT, UK
Telephone: +44 29208 79182 Fax: +44 2920874030 Email KnowlesPJ at Cardiff.ac.uk
WWW http://www.cardiff.ac.uk/chemy/contactsandpeople/academicstaff/knowles.html

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