The projected density of state is a representation of the electronic structure of a material or system. It provides information on the number of available electronic states at different energy levels, and their contributions from different atomic orbitals or groups of atoms.
The projected density of state is calculated using quantum mechanical methods, specifically density functional theory (DFT). It involves solving the Schrödinger equation for the electronic wavefunction of the system, and then integrating the square of this wavefunction to obtain the electron density. This density is then projected onto the atomic orbitals or groups of atoms of interest.
The projected density of state provides important information about the electronic properties of a material, including the energy levels of the electronic states, their occupation, and their contributions from different atomic orbitals. This information can be used to understand the bonding, electronic conductivity, and other electronic properties of the material.
The total density of state is a representation of the electronic structure of a material or system as a whole, while the projected density of state focuses on the contributions from specific atomic orbitals or groups of atoms. Therefore, the projected density of state provides more detailed information about the electronic properties of a material, while the total density of state gives a broader overview.
The projected density of state can be measured using a variety of experimental techniques, including x-ray photoelectron spectroscopy, scanning tunneling microscopy, and angle-resolved photoemission spectroscopy. These techniques involve exciting and detecting electrons from the material, and analyzing their energy and momentum to determine the projected density of state.