Tag Archives: Crystal structure

Sartorite

Sartorite

  • Named after Wolfgang Sartorius von Waltershausen (1809 – 1876) Professor of Mineralogy, University of Göttingen, Germany. He was the first who described the mineral.
  • Formula: PbAs2S4
  • Space group: P21/(No. 14)
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 19.62 Å, b = 7.89 Å, c = 4.19 Å, α = γ = 90°,  β = 90° (!)

Picture: Rob Lavinsky, iRocks.com – CC BY-SA-3.0


Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • PbS9 polyhedra (gray)
  • AsS3 trigonal pyramids (green)
  • Sulfur (yellow)

For a 3D interactive version on sketchfab, see here:

https://skfb.ly/6IYWO

Portlandite – basis for a very important building material

Portlandite

  • Named portlandite because it is a common product of hydration of portland cement
  • Formula: Ca(OH)2
  • Space group: P-3m1 (No. 164)
  • Crystal system: trigonal
  • Crystal class: -3 2/m
  • Lattice parameters: a = b = 3.5918 Å, c = 4.9063 Å, α = β = 90°, γ = 120°

Picture (public domain): SEM image of fractured hardened cement paste, showing plates of calcium hydroxide and needles of ettringite


Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • CaO6 octahedra (blue)
  • Oxygen (red)
  • Hydrogen (white)

For a 3D interactive version on sketchfab, see here:

https://skfb.ly/6ItSG

Ice IV – a remarkable self-interpenetrating structure

Ice IV (Ice four)

  • metastable in the phase space between Ice III, Ice V and Ice VI (see orange circle in the Figure above)
  • may be formed from high-density amorphous ice by slow heating from 145 K and a constant pressure of 8 kbar
  • calc. density at 110 K and 1 bar = 1.27 g/cm3

Structural features

  • proton-disordered phase
  • all water molecules are hydrogen-bonded to four others, two as donor and two as acceptor
  • exclusively 6-membered rings (two types, one almost flat, the other more puckered)
  • the most striking structural feature is that Ice IV builds a self-interpenetrating structure, but this does not consists of two independent networks but of only one net: two water molecules (shown in blue in the following Figure) bonded by H-bonds are oriented perpendicular and are running through the center of the almost flat 6-membered rings:

  • Space group: R-3c (No. 167)
  • Crystal system: trigonal
  • Lattice parameters:
    • a = b = 8.72922 Å, c = 17.06581 Å
    • α = β = 90°, γ =120°

 Here, you can download the CIF.

Literature:

[1] H. Engelhardt and B. Kamb, Structure of ice IV, a metastable high-pressure phase, Journal of Chemical Physics 1981, 75, 5887-5899. DOI: 10.1063/1.442040

[2] C. G. Salzmann, I. Kohl, T. Loerting, E. Mayer and A. Hallbrucker, Raman spectroscopic study on hydrogen-bonding in recovered ice IV, Journal of Physical Chemistry B 2003, 107, 2802-2807. DOI: 10.1021/jp021534k

 

[Atomistic structure figures created with

VESTA
K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).

and

CrystalMaker®.]

Ice III and IX

Ice III and IX (Ice three and Ice nine)

  • Ice III can be formed from liquid water at 300 MPa (3000 bar) by lowering the temperature to approx. 250 K.
  • The relative permittivity is very high (~ 117)
  • Density: 1.16 g/cm3

Structural features

  • Ice III is also called Keatite Ice, because the oxygen atoms are located at analogous positions of the silicon atoms in the SiO2 phase Keatite.
  • Ice IX is the proton-ordered form of Ice III.
  • The tetrahedral environment of the water molecules are considerably distorted.
  • Interestingly, there are no 6-membered rings present anymore, but 5, 7, and 8 –membered rings instead. The 5-membered rings can be best seen if you look along the a or b direction:

 

    • Two-third of the water molecules are forming 41 helices/screws running along the c axis, which means that Ice III is chiral! The other water molecules connect these helices and are forming a 21 helix.

 

  • Space group: P41212 (No. 92)
  • Crystal system: tetragonal
  • Lattice parameters:
    • a = b = 6.73(1) Å, c = 6.83(1) Å
    • α = β = γ = 90°

 

 Here, you can download the CIF.

[Atomic structure figures created with

VESTA
K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).

and

CrystalMaker®.

Celestial Celestine

Celestine

  • named from the Latin word caelestis meaning celestial, which in turn is derived from the Latin word caelum meaning sky or heaven because of its often soft blue color
  • pure Celestine is colourless
  • due to lattice defects in Celestine, colour centres are created which give the crystal its characteristic bluish colour
  • these centers are often additionally stabilized by the presence of pottasium ions
  • heating to over 200 °C “cures” these lattice defects and the mineral loses its color
  • radiation with X-rays creates new or more lattice defects and the color returns or can be intensified.
  • Formula: SrSO4
  • Space group: Pnma (No. 62)
  • Crystal system: orthorhombic
  • Crystal class: mmm
  • Lattice parameters:  a = 8.360 Å, b = 5.352 Å, c = 6.858 Å, αβγ = 90°

Picture: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0


Crystal structure (click on the pictures to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • SO4 tetrahedra (yellow)
  • SrO8 polyhedra (green)
  • Oxygen (red)

For a 3D interactive version, see here:

https://skfb.ly/6zG6R

Ice II (Ice-two)

Ice II (Ice two)

  • can be formed from hexagonal Ice (Ice Ih) at 198 K and 3000 bar or by decompressing Ice-five (Ice V) at 238 K
  • Ice II is likely to be a major rock-forming mineral in the outer Solar System
  • It may form a major proportion of icy moons such as Jupiter’s Ganymede
  • Density: 1.16 g/cm3

Structural features:

  • Ice-two is a proton-ordered form of ice
  • there are two types of 6-membered rings; one is almost flat (Type A) the other one has a more puckered, chair-like conformation (Type B)
  • these two types of rings are strictly alternating stacked along the c axis

  • If you look along the c axis, you will see that the two types of 6-rings are slightly rotated against each other (~ 16 degrees)

  • Space group R-3
  • Lattice parameters:
    • a = b = 12.935 Å, c = 6.233 Å
    • α = β = 90°γ = 120°

  Here, you can download the CIF.

[Atomic structure figures created with VESTA:
K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr.44, 1272-1276 (2011).]

Eucryptite – not an altcoin but millionfold used in the kitchen

β-Eucryptite

  • Named from the Greek for “well” and “concealed”, in reference to its occurrence as intimate intergrowths with the mineral albite
  • It is the main component of the fameous glass-ceramic cooktops for stoves, known in the EU under the trademark Ceran® from Schott AG
  • Formula: LiAlSiO4
  • Space group: P6222 (No. 180)
  • Crystal system: hexagonal
  • Crystal class: 622
  • Lattice parameters: a = b = 10.500 Å, c = 11.194 Å, αβ = 90°, γ = 120°

Crystal structure (click on the picture to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • SiO4 tetrahedra (orange)
  • AlOtetrahedra (light blue)
  • Li (purple/pink)
  • Oxygen (red)

For a 3D interactive version, see here:

https://skfb.ly/6wqY9