Unit Cell Density Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Chemistry & Materials

Tranche

tranche-5

Evidence ID

t5-047

Ledger rows

1

No ledger note is attached.

Review findings

The instrument should be labeled as calculating ideal theoretical crystal density, not measured bulk density. Before release, specify the cell convention, validate structure/Z consistency, define the packing-factor formula, and require explicit units for lattice parameter, molar mass, and density.

Formula and scope findings

• The density formula ρ=(Z·M)/(Vcell·NA) is standard, provided Z is the number of atoms in the selected unit cell and M is molar mass.
• The specification does not define Vcell. For conventional cubic SC, BCC, and FCC cells, Vcell=a^3; this assumption must be stated explicitly.
• The output includes packing factor, but no packing-factor formula is supplied. Under the hard-sphere conventional-cell model, the standard values are SC=π/6≈0.523599, BCC=π√3/8≈0.680175, and FCC=π/(3√2)≈0.740480.
• The inputs redundantly specify both crystal structure type and Z without requiring consistency. Enforce SC→Z=1, BCC→Z=2, and FCC→Z=4, or clearly define which input takes precedence.

Unit assumptions

• For vectors using nanometers, a is converted using 1 nm=1.0×10^-7 cm; with M in g/mol, density is reported in g/cm^3.
• For the meter-based vector, a is in meters and M is in kg/mol; density is reported in kg/m^3.
• NA is taken exactly as the supplied value 6.022×10^23 mol^-1 for these calculations.
• The stated lattice parameter is the edge length of a conventional cubic unit cell.
• Packing factor assumes identical hard-sphere atoms in the conventional cubic cell.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

An extreme but representable lattice parameter of 1.0×10^-300 m causes JavaScript exponentiation to underflow a^3 to zero, producing Infinity instead of a finite density. The unit convention is also hazardous because interpreting a=0.36 as Å rather than nm changes the result by a factor of 1000.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "crystal_structure": "SC",
    "lattice_parameter": 0.3,
    "lattice_parameter_unit": "nm",
    "molar_mass": 40,
    "molar_mass_unit": "g/mol",
    "Z": 1
  },
  "expected_outputs": {
    "theoretical_density": 2.460115,
    "density_unit": "g/cm^3",
    "packing_factor": 0.523599
  },
  "working": "a=0.300 nm=3.00×10^-8 cm. Vcell=a^3=(3.00×10^-8)^3=2.700×10^-23 cm^3. Z·M=1×40.00=40.00 g/mol. Vcell·NA=(2.700×10^-23)(6.022×10^23)=2.700×6.022=16.2594. ρ=40.00/16.2594=2.460115 g/cm^3. PF=π/6=0.523599."
}

Related workflows

No source-defined multi-instrument workflow membership is recorded.

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche5/tranche5-results.json
• BOUNDARY_HAZARD_CATALOG.json