ConstantID

Lattice spacing of ideal Si (220)

UnitsMeasured

d220 = 1.920 155 716(32) × 10−10 m

Value
1.920 155 716 × 10−10 m
Standard uncertainty
3.2 × 10−18 m
Relative uncertainty
1.7 × 10−8 (17 parts per billion)
Status
Measured
Symbol
d220
Source
CODATA 2022 via NIST · NIST entry

Use in a calculation

# lattice spacing of ideal Si (220), CODATA 2022 (NIST)
lattice_spacing_of_ideal_si_220 = 1.920155716e-10  # m, standard uncertainty 3.2e-18

# SciPy: scipy.constants.physical_constants['lattice spacing of ideal Si (220)']

What it is

The spacing of the (220) planes in an ideal silicon crystal, a/√8. X-ray interferometers measure it to link X-ray wavelengths with the metre.

In other units

UnitValue
CGS (cm)1.920 155 716 × 10−8
nm nanometre0.192 015 5716
pm picometre192.015 5716
fm femtometre192 015.5716
Å ångström1.920 155 716
a₀ bohr (atomic unit)3.628 568 422unit is itself measured

Converted with ConstantID's unit table; digits are rounded to the precision of the value, and a long exact value is rounded only for display. The relative uncertainty is unchanged by conversion to an exactly defined unit.

How the value changed, 1998–2022

Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart).

lattice spacing of ideal Si (220): CODATA values 1998–2022 relative to the 2022 value, in parts per billion, with one-standard-uncertainty bars−200−1000+100+200parts per billion1998200220062010201420182022

Relative uncertainty

lattice spacing of ideal Si (220): relative standard uncertainty in each CODATA adjustment, logarithmic scale10⁻⁹10⁻⁸10⁻⁷1998200220062010201420182022
CODATAValue (uncertainty)Relative uncertaintyChange from previous
20221.920 155 716(32) × 10−101.7 × 10−8 +0.0 σ of 2018
20181.920 155 716(32) × 10−101.7 × 10−8 +0.1 σ of 2014
2014192.015 5714(32) × 10−121.7 × 10−8 +0.0 σ of 2010
2010192.015 5714(32) × 10−121.7 × 10−8 −1.0 σ of 2006
2006192.015 5762(50) × 10−122.6 × 10−8 −2.9 σ of 2002
2002192.015 5965(70) × 10−123.6 × 10−8 +2.1 σ of 1998
1998192.015 5845(56) × 10−122.9 × 10−8

“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).