Variational grand-canonical electronic structure method for open systems

Shlomit Jacobi, Roi Baer*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


An ab initio method is developed for variational grand-canonical molecular electronic structure of open systems based on the Gibbs-Peierls-Boguliobov inequality. We describe the theory and a practical method for performing the calculations within standard quantum chemistry codes using Gaussian basis sets. The computational effort scales similarly to the ground-state Hartree-Fock method. The quality of the approximation is studied on a hydrogen molecule by comparing to the exact Gibbs free energy, computed using full configuration-interaction calculations. We find the approximation quite accurate, with errors similar to those of the Hartree-Fock method for ground-state (zero-temperature) calculations. A further demonstration is given of the temperature effects on the bending potential curve for water. Some future directions and applications of the method are discussed. Several appendices give the mathematical and algorithmic details of the method.

Original languageAmerican English
Article number044112
JournalJournal of Chemical Physics
Issue number4
StatePublished - 2005

Bibliographical note

Funding Information:
This work was supported by the Israel Science Foundation. We thank Professor Ronnie Kosloff for stimulating discussions.


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