Quantum chemical tree code

Challacombe, M., Schwegler, E., Almlof, J., 1996, Fast Assembly of the Coulomb Matrix A Quantum Chemical Tree Code , J. Chem. Phys., 104, 4685. 

Challacombe, M. E. Schwegler, and J. Almlof. 1996. Fast assembly of the Coulomb matrix A quantum chemical tree code. J. Chem. Phys. 104,4686. 

The quantum-chemical tree code (QCTC) [M. Challacombe and E. Schwegler, J. Chem. Phys., 106, 5526 (1997)] is a modification of the classical tree-code method. The QCTC method allows calculation of the matrix elements of the Coulomb matrix J for large molecules in a time that is proportional to the number of basis functions b this calculation is 0 b), and one says that the calculation exhibits linear scaling with size of the molecule. Challacombe and Schwegler used the QCTC method to do an ab initio SCE MO calculation on the 698-atom monomer of the P53 protein at a fixed geometry (obtained from a protein data bank) using the 3-21G basis set (3836 basis functions). They then calculated the molecular electrostatic potential (Section 15.7) of the P53 monomer. (The P53 protein is a tetramer and acts as a tumor suppressor. Mutations in the gene for this protein are found in half of human cancers.)... 

Assembly of the Coulomb Matrix A Quantum Chemical Tree Code. 

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