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Distinctive from conventional electronic structure methods, we solve the Schrödinger wave equations of the helium atom and its isoelectronic ions by employing one-dimensional basis functions to separate components. We use full two-electron six-dimensional operators and wavefunctions represented with real-space grids where the refinement of the latter is carried out using a residual minimization method. In contrast to the standard single-electron approach, the current approach results in exact treatment of repulsion energy and, hence, more accurate electron correlation within five centihartrees or better included, with moderate computational cost. A simple numerical convergence between the error to accurate results and the grid-spacing size is found. The obtained two-electron Schrödinger wavefunction that contains vast and elaborating information for the radial correlation function and common one-dimensional functions shows the electron correlation effect on one-electron distributions. [ABSTRACT FROM AUTHOR]

First-principlescalculations based on density functional theory have been performedto explore the stable configurations, electronic structures, and vibrationalspectra of neutral and charged silicon monoxide clusters (SiO)n(0,±)(n= 2–7), which could be used as precursors in the synthesisof silicon nanowires. Our theoretical calculations provide new resultson characteristic electron affinity, ionization potential, and vibrationalspectroscopy, guiding future experiments in the synthesis of high-qualitysilicon nanowires. Specifically, as the number of SiO units nincreases, IR spectra of (SiO)n±and Raman spectra of (SiO)n–show an evident blue shift, and Raman spectraof (SiO)ndemonstrate a red shift. Moreover,most of the neutral silicon monoxide clusters have strong IR intensitiesand weak Raman activities, while most of the anionic counterpartshave relatively weak IR intensities and strong Raman activities. Someother energetically competitive isomers of some (SiO)n(0,±)species were also studied forcomparison. [ABSTRACT FROM AUTHOR]