4.2 PDOS and charge density: projections are not unique atoms

These are unexecuted teaching inputs and starting models. Original diagrams are schematics, not calculated results. Validate version-specific syntax, licensed or authorized data, numerical convergence and the scientific model before using this workflow.

4.2.1 Model, units and provenance

PW cutoffs and energies use Ry, common force output uses Ry/bohr, and pressure uses kbar. Geometry cards state their coordinate units. Different executables have distinct grammars and time-unit conventions.

Shared inputs, conventions and evidence

Original schematic: PDOS and charge density: projections are not unique atoms. No numerical results are claimed.

4.2.2 Unexecuted inputs and explicit deltas

Use the accompanying instructions to identify the parent calculation and placement of every delta; a snippet is not automatically a standalone input. Preserve all blank-line and file-provenance requirements.

4.2.2.1 Input block 1

&PROJWFC
 prefix='si', outdir='./scratch/si_dos', filpdos='si.pdos',
 Emin=-10.0, Emax=10.0, DeltaE=0.02, degauss=0.01
/

4.2.2.2 Input block 2

&INPUTPP
 prefix='si', outdir='./scratch/si', filplot='si.rho', plot_num=0
/
&PLOT
 nfile=1, filepp(1)='si.rho', weight(1)=1.0,
 iflag=3, output_format=6, fileout='si.rho.cube'
/

4.2.3 Worked investigation

4.2.3.1 Intuition and prerequisites

PDOS answers how much a state resembles chosen local orbitals; it does not uniquely partition electrons into atoms. Charge density is a real-space field with its own normalization and pseudopotential conventions. Reuse the dense Si NSCF for PDOS and its matching SCF for density. Do not mix grids or structures when comparing fields.

4.2.3.2 Original post-processing inputs

See input block 1 above.

4.2.3.3 Checks, pitfalls and exercise

Sum selected projections and compare with total DOS while retaining the projection spilling information; imperfect closure is informative, not necessarily a failed calculation. Integrate the density with the correct voxel volume and compare with the expected represented electron count. An isosurface changes appearance with its threshold, so report that threshold. Exercise: plot the same density with two isovalues and explain what is invariant; compare s/p projected weight without labeling it an integer oxidation state.