PMID- 16164336
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20070815
LR  - 20050916
IS  - 0021-9606 (Print)
IS  - 0021-9606 (Linking)
VI  - 123
IP  - 9
DP  - 2005 Sep 1
TI  - Towards accurate all-electron quantum Monte Carlo calculations of 
      transition-metal systems: spectroscopy of the copper atom.
PG  - 94102
AB  - In this work we present all-electron fixed-node diffusion Monte Carlo (FN-DMC) 
      calculations of the low-lying electronic states of the copper atom and its 
      cation. The states considered are those which are the most relevant for the 
      organometallic chemistry of copper-containing systems, namely, the (2)S, (2)D, 
      and (2)P electronic states of Cu and the (1)S ground state of Cu(+). We 
      systematically compare our FN-DMC results to CCSD(T) calculations using very 
      large atomic-natural-orbital-type all-electron basis sets. The FN-DMC results 
      presented in this work provide, to the best of our knowledge, the most accurate 
      nonrelativistic all-electron correlation energies for the lowest-lying states of 
      copper and its cation. To compare our results to experimental data we include the 
      relativistic contributions for all states through numerical Dirac-Fock 
      calculations, which for copper (Z=29) provide almost the entire relativistic 
      effects. It is found that the fixed-node errors using Hartree-Fock nodes for the 
      lowest transition energies of copper and the first ionization potential of the 
      atom cancel out within statistical fluctuations. The overall accuracy achieved 
      with quantum Monte Carlo for the nonrelativistic correlation energy (statistical 
      fluctuations of about 1600 cm(-1) and near cancelation of fixed-node errors) is 
      good enough to reproduce the experimental spectrum when relativistic effects are 
      included. These results illustrate that, despite the presence of the large 
      statistical fluctuations associated with core electrons, accurate all-electron 
      FN-DMC calculations for transition metals are nowadays feasible using extensive 
      but accessible computer resources.
FAU - Caffarel, Michel
AU  - Caffarel M
AD  - Laboratoire de Physique Quantique, IRSAMC Universite Paul Sabatier, 118 route de 
      Narbonne, 31062 Toulouse Cedex, France. caffarel@irsamc.ups-tlse.fr
FAU - Daudey, Jean-Pierre
AU  - Daudey JP
FAU - Heully, Jean-Louis
AU  - Heully JL
FAU - Ramirez-Solis, Alejandro
AU  - Ramirez-Solis A
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Chem Phys
JT  - The Journal of chemical physics
JID - 0375360
EDAT- 2005/09/17 09:00
MHDA- 2005/09/17 09:01
CRDT- 2005/09/17 09:00
PHST- 2005/09/17 09:00 [pubmed]
PHST- 2005/09/17 09:01 [medline]
PHST- 2005/09/17 09:00 [entrez]
AID - 10.1063/1.2011393 [doi]
PST - ppublish
SO  - J Chem Phys. 2005 Sep 1;123(9):94102. doi: 10.1063/1.2011393.