Density matrix Quantum theory 16 Matrix algebra 12 Molecular systems 10 Electrons 6 Atomic domains 4 Atoms 4 Chemical bonds 4 Chemical descriptors 4 Convexity properties 4 Eigenvalues and eigenfunctions 4 Electron system 4 Many electron 4 Molecular dynamics 4 Molecules 4 Number of electrons 4 Physical chemistry 4 Physics 4 Reliability 4 Spatial decomposition 4 Theoretical aspects 4 reduced density matrices 4 Algebraic structures 2 Analytical model 2 Angular momentum 2 Atomic orbital 2 Convex functions 2 Correlated wave functions 2 Correlation detectors 2 Correlation effect 2