In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid.

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Etching around corners

In etching of mono silicon, why does the etching process around the corners differ from the etching process around the flat edges? What brings about this difference and is there some way that MEMS ...
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How do I make PDB 1HIG's data usable for producing ball-and-stick models?

PDB: 1HIG, when opened using Accelrys DS Visualizer, Avogadro and Jmol produces a series of dots in space and cannot be displayed as 3D ball and stick models. Is there any way to overcome this ...
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Is it possible to construct a 3D molecular model using x-ray powder diffraction data?

I've got x-ray powder diffraction (XRPD) data on bendamustine HCl from a patent and I want to know how to construct a 3D model using this data with software.
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Are the native starch's structure and properties different from retrograded starch?

Starch gelatinization occurs when native starch is being expose to heat and water. Gelatinized starch then can be retrograded under cool temperature. But the structure and properties of retrograded ...
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crystalline structure of Si wafers used for MEMS

When they say that we have a {1 0 0} single crystal wafer, I know that the surface normal to the wafer is oriented in the <1 0 0> family direction, but if I draw a line on the wafer, parallel to my ...
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Is it possible to infer the structure of hydroxychloroquine based on the crystal structure of chloroquine?

I've been trying to construct an experimentally-based structure of hydroxychloroquine based on the crystal structure of chloroquine, as depicted by PDB: 1CET (R-enantiomer) and PDB: 4FGK ...
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How is the crystal direction important for etching silicon surfaces?

I am a student of masters study with a background only in electrical engineering, but I have studied Miller indices and crystallographic planes and directions, personally, to help myself understand ...
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25 views

Where is the center of symmetry in the PbO crystal?

I'm very confused as to where the center of symmetry is for the PbO (litharge form). I know that it is in the P4/nmm space group, and that it's centrosymmetric, but beyond that I'm clueless. Thank ...
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Binding forces in crystalline solids

I am referring to rocks in this instance. Individual crystals grow together in an igneous rock as it solidifies. I know that the $\ce{SiO4}$ tetrahedron is the basic building unit of silicate ...
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Cubic lattice: How corner atom of a cube is shared by 8 atoms

Since ,"Each atom is at the corner of a cube and 8 cubes meet at each corner. Therefore each atom is shared by 8 cubes." But i don't visualize it ,so please tell how i Visualize it .
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How to predict the type of intrinsic defect?

How do we predict the type of intrinsic defects in materials. For example what are the intrinsic defects in $\ce{HgSe}$ and $\ce{Ba3N2}$ ?
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XRD-Shorter distance between planes than actual radius of atoms/or cell parameter

I'm solving problems related to X-ray diffraction, and I get these results which apparently are correct. My question may be dumb, but I just can't see how the interplanar distance might be shorter ...
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66 views

How do I write a valid CIF, PDB or XYZ file from the coordinates listed below?

I want to create a 3D molecular file using coordinates taken from: Hrynchuk, RJ; Barton, RJ; Robertson, BE (1983). "The crystal structure of free base cocaine, C17H21NO4" (PDF). Canadian Journal of ...
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Empirical formula of Berthollides

Can the empirical formula be defined for berthollides? Is it equal to the molecular formula, or it can't be defined?
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Miller indices. What determines the appropriate axis?

So, first of all, what's up with this "plane" I see two planes! The basis of my question is that to determine miller indices the plane cannot lie on your origin, so you have to make a translation. ...
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Central Atom in EXAFS

I read somewhere that EXAFS (Extended X-ray absorption fine structure) gives us the distances between central atom and its neighboring atoms. Is that true? Why can't we get the distance between two ...
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Two-dimensional Networks of Coordination Polyhedra

Does anyone know of any references that use {V/P, P/V} notation? This involves polyhedra joining to form polygons, or vice versa (this is where my confusion lies) V/P may refer to the number of ...
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75 views

Determining perovskite crystal structure

I've been reading that perovskite presents a sort of pseudocubic crystalline system, however it can be stretched and suffer modifications to become orthorhombic etc. The thing is, if I consider it ...
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What's the most efficient way to find crystal structures of drugs?

I'd like to be able to find the crystal structures of drugs, for example at the moment I want to find the crystal structure of (R)-fluoxetine so that I can use Jmol to create an accurate 3D model of ...
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Determining the Packing Geometry of Compounds

I'm a little confused on the method to determine packing geometry. The question I'm given is Determine the packing geometry of the following compounds by using the radius ratio rules. For your ...
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Carbon atoms at the edge of a diamond

It is well known (the simplest textbook example) that a diamond has a well-defined arrangement of sp3 carbon atoms, as each atom is connected to four others in a ...
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Approach to model solvent in a lattice: e.g. H2O in NaCl

If a lattice contains a solvent, lets say NaCl and water of crystallisation, what is the condition for a solvent molecule to change it's location? From my current point of view I assume that such a ...
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58 views

Grocery store crystalline citric acid

Which type of citric acid crystalline powder do they sell in grocery stores? Is the concentration of citric acid in the crystals 100%?Is it anhydrous or a monohydrate?
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Represent bonds spanning a unit cell boundary plane

Is there a chemical input format that is- Supported by Open Babel (and hence supports visualization in avogadro??) Can represent a bond connecting an atom to its partner in a neighbouring unit cell, ...
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What happens when ice melts?

What happens when ice melts? I have this question, with two possible answers: regularly arranged molecules change into irregularly arranged molecules water molecules become less densely packed ...
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how to determine timescale with characterization methods?

There are as classified in the Atkins textbook 4 different timescales on material characterization: a)Time during which a quantum of radiation or a particle can interact with a molecule. b)Lifetime of ...
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Dihedral angle of gaseous and crystalline HOOH

Why does hydrogen peroxide exhibit a dihedral angle of 111.5 degrees in the gaseous state? And a dihedral angle of 90.2 degrees in the crystalline phase? I know that in general, there is likely to ...
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Is there a systematic way to determine the expected cubic structure of metals?

I've noticed that some groups of metals with similar properties tend to belong to the same cubic structure group, such as $\text{FCC, BCC, or HCP}$. What is a good explanation as to why these metals ...
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How do people check the type of defect in a crystal?

There are many types of defects like Vacancy Interstitial Schottky Frenkel Non-Stoichiometric Alien Impurities But given a sample, how do scientists know which kind of defect is present in it ...
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What is the length of a unit cell of CuCl assuming that it is fcc?

The density of CuCl is given - x gm/cmm The crystal structure is assumed to be fcc. My teacher is claiming the we can apply the formula $$\rho=\frac{Z * M}{a^3 * N_0}$$ And he took M = 35.5+63.5gm = ...
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Structure of diamond

"diamond structure. Every carbon atom is bonded to four other carbon atoms forming a three-dimensional lattice of chair conformations." SENTENCE FROM A BOOK What does this mean? Where I am struck ...
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What are Lattice Points

What are lattice points exactly? And Also How many Lattice Points are there in each of the Unit Cells?
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What are these crystals on my champagne cork?

I opened up a bottle of champagne that was left in a wine cooler for approx. 8 years. To my astonishment there were small crystals at the underside of the cork. The crystals are colorless, odorless ...
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Crystal structure in function of pressure

If you were to investigate crystal structure changes as a function of pressure, which metals would you study first? Last? Why?
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Elementar cell of Y2O3

I think this picture from wikipedia is wrong because I count: \begin{align} \left. \begin{array}{ccccr} 1&×&1 &= &\ce{1~Y} \\ 6&×&\frac{1}{8} &= &\ce{\frac{3}{4}O} ...
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Is BCl₅ possible?

Is $\ce{BCl5}$ possible? I saw it in book. As far as we can see there is no way to get 5 chlorine atoms with boron.
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If salt crystals make a cube shape, what is this 'X' marking?

I am an amateur, with very little professional chemistry knowledge. I was doing a demonstration / experiment with my 6 year old child. We took very warm normal tap water, and dissolved into it a ...
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Chemical bonding - lattice energy

Question: Why is ionic lattice energy inversely proportional to the radius of the atom? Most heterogeneous covalent molecules are polar to some extent. The degree of polarity, or the dipole moment, ...
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Polymer Crystallinity

See the following question: I think the answer is A because of the hydrogen bond in the side group, thus the degree of secondary bonding between parallel chain segments is higher. Is my thinking ...
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How does the crystal know where to stop stacking the unit cells?

I tried to make different crystals in the cubic system by stacking cubes in a 3d software. However I need to tell the software where to skip rows or stop stacking the unit cells in a specific ...
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How do we know the size of atoms in body centered cubic system?

I'm told that in the normal cubic system there are $\frac18$ of an atom at each corner and these atoms' radius are such that $a = 2r$ ($a$ is the lattice constant, $r$ radius of an atom). In bbc ...
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Are metallic/ionic bonds weaker than covalent bonds? I was taught the opposite. Now I'm confused

In mineralogy class, I was taught that metallic and ionic bonds are weaker than covalent bonds and that's why quartz and diamond have such a high hardness value. However, in organic chemistry class, I ...
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Why do NaHCO₃ and KHCO₃ have different crystal structures?

Why do $\ce{NaHCO3}$ and $\ce{KHCO3}$ have different crystal structures? We had this in a test today and this got me stumped... My questions are: Do $\ce{NaHCO3}$ and $\ce{KHCO3}$ possess ...
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Bonding, multiplicity and quantum chemistry for FeP$_2$

I'm trying to do some quantum chemical calculations for the linear molecule FeP$_2$ in the gas phase as well as its crystal (orthorhombic symmetry like here). I am lead to believe that in both cases ...
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How to determine mineral properties based on chemical formula?

I need to learn a bunch of minerals and their properties. What I want is some sort of rule which helps me deduce color, crystal system, luster etc. I know that different kind of ions give specific ...
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244 views

How to memorize 7 crystal systems?

Is there any trick to memorize the angles and sides of 7 crystal systems of crystalline solids? 1. Cubic 2. Tetragonal 3. Orthorhombic 4. Monoclinic 5. Hexagonal 6. Rhombohedral or Trigonal 7. ...
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What is the minimum distance of Rubidium and Iod ions in a centered cube?

I have a problem to visualize the following assignment: What is the minimum distance between $\ce{Rb^+}$ and $\ce{I^-}$ ions if radius of $\ce{Rb^+}$ is ${1.49\cdot10^{-10}}~\mathrm{m}$ and radius ...
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How many Ga atoms are connected to one As atom in solid state Gallium arsenide

Let's start straight away. In this book on page 4 Gallium arsenide's bond structure is shown like this: $As$ is shown making $5$ covalent bonds. Recently I came across this book. The bond structure ...
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Hexagonal unit cells

I know 3 types of unit cells, the simple cubic, the body centered and the face centered. But what is a hexagonal unit cell, and why does it have a hexagon base while others are all cut into a cubic? ...
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Why is there one octahedral and two tetrahedral positions for every anion in a close packed structure?

I'm reading about ionic crystal structures with planes of close-packed anions and the interstitial sites for cations. There are two types of interstitial sites: tetrahedral and octahedral. That makes ...