Periodic Model Build-up Outline • Learn about crystals… (HW) • Learn about Materials Studio… • Search ICSD/CSD/PDB if necessary… • Import several crystals using Materials Studio… • Build CNT using Materials Studio… • Move to Room #310 & Do It Yourself!
42
Embed
Periodic Model Build-up Outline Learn about crystals… (HW) Learn about Materials Studio… Search ICSD/CSD/PDB if necessary… Import several crystals using.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Periodic Model Build-up
Outline
• Learn about crystals… (HW)• Learn about Materials Studio…• Search ICSD/CSD/PDB if necessary…• Import several crystals using Materials Studio…• Build CNT using Materials Studio…• Move to Room #310 & Do It Yourself!
Lab examples
• Pure crystal [Si, Ag, Au]
• Alloy [Co/Tb, Fe/Si]
• Oxide [TiOx]
• Boride [TmB4, TmAlB4]
• CNT, C60, diamond & their derivatives [PCBM]
• Organic & Polymer [P3HT, PQT, PSS, PEDOT]
& their surfaces, interfaces, composites, defects, …
################################################################################ Noreus, D.Werner, P.-E. (1982)# Acta Chemica Scandinavica, Series A: (28,1974-) 36, 847-851# Structural studies of hexagonal Mg2 Ni Hx# # CIF by ICSD-for-WWW, Copyright 2003 FIZ-Karlsruhe & A.W.Hewat ([email protected])# NOT TO BE PUBLISHED IN ANY FORM. See http://icsd.ill.fr/icsd/conditions.html###############################################################################
• Fractional coordinates (in crystals) {xA/a, yA/b, zA/c}
• Cartesian coordinates {xA, yA, zA}
• Z-matrix (internal coordinates) {rA, A, A}
Crystal (Periodic Structure w Translational Symmetry)
1
m3m
4/mmm
mmm
6/mmm 3m
2/m
Au, Ag, Pt, Cu, Ni, Pd, etc.
Fe, V, K, Bi, etc.
Ru, Be, La, etc.
Im3m
Fm3m
P63/mmc
Crystal Structure
Carbon Nanotube (CNT)
Step 1 : Identify the intercepts on the x- , y- and z- axes. Intercepts: a,, Step 2 : Specify the intercepts in fractional coordinates. Fractional intercepts: 1,, Step 3 : Take the reciprocals of the fractional intercepts. Reciprocals: 1,0,0
Miller Index (Uniquely identifies planes or surfaces)Practive with a simple cubic crystal
Coordinates are converted to fractional coordinates by dividing by the respective cell-dimension. (Example) A point (x,y,z) in a unit cell of dimensions a x b x c has fractional coordinates of (x/a, y/b, z/c).
(100)
(110)(111)
(211)
fcc unit cell (100) face
fcc unit cell (110) face
fcc unit cell (111) face
bcc unit cell (100) face
bcc unit cell (110) face
hcp unit cell (0001) face
High Miller Index surfaces: most likely terraces + steps
fcc(775)
Even single crystal surfaces will not exhibit the ideal geometry of atoms to be expected by truncating the bulk structure of the solid parallel to a particular plane.
Difference between the real structure and the ideal structure• may be imperceptibly small (surface relaxation ) • may be much more marked and involve a change in the surface periodicity (surface reconstruction )
* Adsorbate-induced reconstruction
Surface Reconstruction
Si(100)-(2x1) reconstruction
Si(100) c(2x4) imaged at T = 120 K. At temperatures < 150 K the dimer row reconstruction of Si(100) is replaced by the honeycomb pattern of the c(2x4)-reconstruction (2nd order phase transition (2x1)c(2x4)). (20 nm x 20 nm)
Si(111)-(7x7) reconstruction
Adsorption Coverage (Packing)
Surface Overlayer: Wood’s notation
fcc (100) face fcc (110) face fcc (111) face
fcc (100) face
fcc (110) face
fcc (111) face
Surface Overlayer: Matrix notation
fcc (100) face fcc (111) face
O(1-fold) O(1-fold)B(2-fold) B(2-fold)
fcc H(3-fold)
hcp H(3-fold)
H(4-fold)
hcp (0001) face
Adsorption Sites
CH3S/Au(111)
A variety of imperfectionscan also afflict single crystals
Point defects
A variety of imperfectionscan also afflict single crystals