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Ministerio de EconomÃa y Competitividad (Espanya)
Ministerio de Ciencia e InnovaciÃ³n (Espanya) 

RamosCordoba, Eloy
Salvador Sedano, Pedro Piris, Mario Matito i Gras, Eduard 

We suggest new strict constraints that the twoparticle cumulant matrix should fulfill. The constraints are obtained from the decomposition ofã€ˆÍˆÅœÂ²ã€‰, previously developed in our laboratory, and the vanishing number of electrons shared by two noninteracting fragments. The conditions impose stringent constraints into the cumulant structure without any need to perform an orbital optimization procedure thus carrying very small or no computational effort. These constraints are tested on the series of Piris natural orbital functionals (PNOF), which are among the most accurate ones available in the literature. Interestingly, even though all PNOF cumulants ensure correct overall ã€ˆÍˆÅœÂ²ã€‰ values, none of them is consistent with the local spin structure of systems that dissociate more than one pair of electrons. A careful analysis of the local spin components reveals the most important missing contributions in the cumulant expression thus suggesting a means to improve PNOF5. The constraints provide an inexpensive tool for the construction and testing of cumulant structures that complement previously known conditions such as the Nrepresentability or the square of the total spin angular momentum, ã€ˆÍˆÅœÂ²ã€‰ This research has been funded by the European Union (EU) under the Marie Curie Career Integration Grant No. PCI09GA2011294240 (E.M.), the Spanish MINECO Europa Excelencia project CTQ201341236ERC (E.M.), the Spanish MICINN Project Nos. CTQ201123441/BQU and CTQ201123156/BQU, the Eusko Jaurlaritza (SAIOTEK Program SPC13UN005), and by the FEDER Grant No. UNGI084E003 (European Fund for Regional Development). We are grateful for the computational resources granted at the MareNostrum computer of the Barcelona Supercomputing Center 

http://hdl.handle.net/2072/295620  
eng  
American Institute of Physics (AIP)  
Tots els drets reservats  
Electrons
Electrons Spin (FÃsica nuclear) Nuclear spin Moment angular (FÃsica nuclear) Angular momentum (Nuclear physics) 

Two new constraints for the cumulant matrix  
info:eurepo/semantics/article  
Recercat 