### Abstract

It is argued that the matrix PS is to be considered as the proper linear combination of atomic orbitals (LCAO) representation of the first-order density matrix, P and S being the usual molecular "density matrix" and the overlap matrix, respectively. This conclusion is in line with the fact that Hermitian operators are represented by non-Hermitian matrices if an overlapping basis is used. (The matrix representation of an operator is to be distinguished from the matrix of its integrals.) The diagonal elements of the matrix PS are Mulliken's gross orbital populations and the elements of this matrix are also necessary to define the bond order between a pair of atoms and the actual total and free valences of an atom in a molecule.

Original language | English |
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Pages (from-to) | 1-7 |

Number of pages | 7 |

Journal | Journal of Molecular Structure: THEOCHEM |

Volume | 255 |

Issue number | C |

DOIs | |

Publication status | Published - Mar 24 1992 |

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### ASJC Scopus subject areas

- Physical and Theoretical Chemistry
- Computational Theory and Mathematics
- Atomic and Molecular Physics, and Optics

### Cite this

**The LCAO representation of the first order density matrix in non-orthogonal basis sets : a note.** / Mayer, I.

Research output: Contribution to journal › Article

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TY - JOUR

T1 - The LCAO representation of the first order density matrix in non-orthogonal basis sets

T2 - a note

AU - Mayer, I.

PY - 1992/3/24

Y1 - 1992/3/24

N2 - It is argued that the matrix PS is to be considered as the proper linear combination of atomic orbitals (LCAO) representation of the first-order density matrix, P and S being the usual molecular "density matrix" and the overlap matrix, respectively. This conclusion is in line with the fact that Hermitian operators are represented by non-Hermitian matrices if an overlapping basis is used. (The matrix representation of an operator is to be distinguished from the matrix of its integrals.) The diagonal elements of the matrix PS are Mulliken's gross orbital populations and the elements of this matrix are also necessary to define the bond order between a pair of atoms and the actual total and free valences of an atom in a molecule.

AB - It is argued that the matrix PS is to be considered as the proper linear combination of atomic orbitals (LCAO) representation of the first-order density matrix, P and S being the usual molecular "density matrix" and the overlap matrix, respectively. This conclusion is in line with the fact that Hermitian operators are represented by non-Hermitian matrices if an overlapping basis is used. (The matrix representation of an operator is to be distinguished from the matrix of its integrals.) The diagonal elements of the matrix PS are Mulliken's gross orbital populations and the elements of this matrix are also necessary to define the bond order between a pair of atoms and the actual total and free valences of an atom in a molecule.

UR - http://www.scopus.com/inward/record.url?scp=8744287575&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=8744287575&partnerID=8YFLogxK

U2 - 10.1016/0166-1280(92)85002-3

DO - 10.1016/0166-1280(92)85002-3

M3 - Article

VL - 255

SP - 1

EP - 7

JO - Computational and Theoretical Chemistry

JF - Computational and Theoretical Chemistry

SN - 2210-271X

IS - C

ER -