Conjugate gradient density matrix search

Millam, J. M., Scuseria, G. E., 1997, Linear Scaling Conjugate Gradient Density Matrix Search as an Alternative to Diagonalization for First Principles Electronic Structure Calculations , J. Chem. Phys., 106, 5569. 

Daniels AD, Milliam JM, Scuseria GE. Semiempirical methods with conjugate gradient density matrix search to replace diagonalization for molecular systems containing thousands of atoms. J Chem Phys 1997 107 425 431. 

Application of the Millam-Scuseria conjugate-gradient density-matrix search method (Section 15.5) to semiempirical methods aUowed single-point AMI energy calculations to be done on a 19995-atom polymer of glydne and a 6304-atom RNA molecule [A. D. Daniels, J. M. Millam, and G. E. Scuseria, /. Chem. Phys., 107,425 (1997)]. 

---