Questions tagged [solid-state-chemistry]

Study of chemical species that are in solid phase, either in cases of their properties, or about ways of synthesizing them.

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27 views

What makes up the conduction band?

Prologue/Rant about online classes We have been taught the electron sea model to explain metallic bonding and conduction of electricity by metals. Then out of the blue, the band theory was introduced, ...
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25 views

Unit cell of hcp structure

It is given in my book that the structure in figure-1 is the unit cell of hcp structure. So why then is the structure in figure-2 not the unit cell as we can repeat the structure in figure-2 to get ...
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51 views

Why is the disordered CuAu structure more stable at high temperatures?

I know that the disordered CuAu structure is based around FCC whereas the ordered CuAu structure is tetragonal. Why would the FCC structure be more stable at high temperatures? For context, I was ...
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1answer
47 views

Getting an “index” of 7 for a Set of Powder Diffraction Data

I know a value of $h^2 + k^2 + \ell^2 = 7$ is not allowed but I cannot understand where I am going wrong with the indexing here. Any insight would be greatly appreciated as I am wondering if this is ...
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2answers
26 views

Coordination number of 3D close packing [closed]

Can anyone explain me that how the coordination number of corner sphere of this 3-D packing is 6 ? it should be 3
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46 views

Why does a covalent solid have a high melting point and boiling point as compared to an ionic solid? [duplicate]

Why does a covalent solid have a high melting point and boiling point as compared to an ionic solid? Shouldn't it be less than that of ionic solids since the coulombic forces in ionic solid is ...
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26 views

How many types of 3D packing are possible?

In my book it's said that there are 3 types of unit cubic cell - primitive , face and body centered . But for 3d packing types they have only mentioned FCC and HCP . I know that these 2 concepts- ...
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1answer
52 views

On the exact definitions of Frenkel and Schottky defects

The wiki page on vacancy defects says; It is also known as a Schottky defect, although in ionic crystals the concepts are not identical. As far as I'm aware, they're the same. Furthermore, the wiki ...
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42 views

Pressure vs electric conductivity in solids

If we apply pressure to a solid, does it change its electric conductivity? I am asking this because in 2020 they announced a superconductor at room temperature but under a pressure of 3/4 of the ...
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1answer
43 views

Height of CCP Lattice

Are the height of the Cubic Close packing Lattice and the cubic Hexagonal Close Packing the same? My understanding says that these unit cells are formed by different arrangement of atoms, ABC for CCP ...
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Why is ruthenium dioxide a conductor while titanium dioxide is an insulator?

Ruthenium dioxide has the same crystal structure as rutile (titanium dioxide), and the metal atoms are in the same oxidation state. Yet ruthenium dioxide is a metal-like conductor (its resistivity is ...
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Degenerate semiconductors /N type dopants/Low fermi level

In extrinsic semiconductors the donor level of some N type dopants is lower in energy than some other dopants . For example as we move from the V to the VIII group if we draw the band diagram the ...
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1answer
108 views

How is Gibbs free energy related to stability? [closed]

I have been learning thermodynamics for quite some time and I fail to relate Gibbs free energy and stability. For example, how do I compare stability of metal oxides using the following data? Also, do ...
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35 views

Interatomic spacing vs electric conductivity

I have a theory which may be wrong but I will write it down.If 2 elements at the same group (in solids)have the same crystal structure then the one with the biggest interatomic spacing has better ...
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23 views

Clarification of term symbol explanation of laser crystal doping from textbook

I am currently studying Diode Lasers and Photonic Integrated Circuits, second edition, by Coldren, Corzine, and Mashanovitch. In chapter 1.2 ENERGY LEVELS AND BANDS IN SOLIDS, the authors say the ...
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2answers
206 views

Silicon–Boron Covalent Bond

This is a semiconductor-related question, but in order to understand the acceptor level energy state of boron in bilicon, I figured I'd ask here for hints. Boron is a p-type material when introduced ...
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1answer
76 views

Is the lattice point in ZnO crystal structure occupied by the molecule ZnO or the ion O^2-/Zn^2+?

I learnt that ZnO has a hexagonal crystal system. I was expecting that cations or anions would occupy the lattice points in hcp while voids would be occupied by anions or cations respectively. But ...
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1answer
72 views

What is the form of the Hamiltonian for solids?

For atoms, and even molecules, I can understand how the Hamiltonian would be constructed, but what of solids (as in, for electronic structure calculations)? Thank you for any help.
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1answer
54 views

Interplanar distance given Miller indice of the planes

Say we've a cubic crystal of unity edge length. A set of planes in such a crystal is specified by their miller indice as $(3 2 0)$. One of these planes then has intercepts on the axes as $(2 ,3 ,\...
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How to calculate planar density of a face /plane of crystal with cation and anions?

Planar density is given by numer of atoms in plane /plane area . Suppose I want to calculate planar density of 100, 101 and 111 planes of Nacl. Radius of Na+ and Cl- ions is 0.086 nm and 0.126 nm.Na+ ...
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24 views

Where are the tetrahedral voids and octahedral voids located in an FCC? [duplicate]

A crystal is made up of atoms X, Y, and Z. Atoms X are in FCC packing, Y occupy all octahedral voids and Z occupies all the tetrahedral voids. If all the atoms along two body diagonal are removed, ...
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1answer
82 views

Ice geometrical shapes [duplicate]

https://en.wikipedia.org/wiki/Ice https://www.google.com/search?q=ice&prmd=inmv&sxsrf=ALeKk028fJvrUcWLWu8EV-KsRGuiw0iWWw:1596098668929&source=lnms&tbm=isch&sa=X&ved=...
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3answers
141 views

Why water cools from outside to inside?

It is a well-known fact that Water kept in a container, on cooling, results in freezing with initially at the circumference of surface (1D), then on the surface (2D) and then throughout the volume (...
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31 views

“e and a” as combinations of pi bonds

I am trying to get a better intuition on solid-state physics but I am a chemist by degree. I came across this article that attempts to bridge the gap between solid-state physics and molecular ...
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How is the Born-Lande equation modified when the structure is not NaCl?

Often the Born-Lande equation is quoted (alongwith the calculation of the Madelung constant and Born exponent) with reference to rock-salt structure. But what if we take some other crystal, like ...
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1answer
24 views

Doping of a solid with impurities [closed]

This question is a continuation of the previous question of mine:press me if you wish And my question is how can I dope a solid with impurities and if the process can be understood with basic ...
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2answers
144 views

How to identify if a material is perovskite or not?

This is more of a materials science question, but I believe many of you have referred NIST Inorganic Crystal Structure Database (ICSD) database. I am collecting a database of perovskite materials and ...
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1answer
161 views

Are HCP and Primitive Hexagonal Unit Cell the same thing? [closed]

In HCP, the [2D] Hexagonal packed layers are arranged in ABAB form. The same happens in Primitive Hexagonal Unit Cell. So does that mean they are the same? If not what differentiates one from the ...
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2answers
246 views

Why rutile structure have primitive unit cell instead of body centered?

In the literature (Wikipedia), I read that $\ce{MgH2}$ have a structure of rutile. Then, I looked at its space group which is $P4_2/mnm$. From this notation, I understood that it possesses a (...
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41 views

Do all metals expand on heating? [duplicate]

This question came up when I was reading about substances with negative thermal expansion. The article by Takenaka [1] gives a good list of materials displaying negative thermal expansion. I noticed ...
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50 views

How can fluorite structure exist?

From the information from Google the radius of $\ce{Ca^2+}$ cation is $100 \,\pu{pm}$ and of $\ce{F-}$ anion is $132\, \pu{pm}$, so essentially $\ce{F-}$ ion should form the Bravais lattice (FCC/CCP) ...
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Reason behind more prioritising of normal spinels

According to my textbook: In normal spinels $\ce{A^{II}}$ should have occupied octahedral voids, but this factor is outweighed by greater lattice energy or smaller cation $\ce{B^{III}}$. Later, ...
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2answers
175 views

Change in the number of ions due to exchanging ions [closed]

If the position of Na+ and Cl- are interchanged in NaCl having FCC arrangement of Cl- ions then what change we can observe in the unit cell of NaCl. I am confused as how the contribution will change ...
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1answer
2k views

Calculate third and fourth nearest neighbours in fcc packing [closed]

My textbook has given data for third and fourth nearest neighbours to be 6 and 8 with distances  a and √(3/2)a. I have been able to calculate for the first and second nearest neighbour but it has ...
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2answers
58 views

Effect of pressure on transition temperature

I was wondering if someone can explain why the answer to the following question is volume instead of the others. If pressure has no effect on the transition temperature between two crystalline forms ...
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1answer
650 views

Is the number of tetrahedral voids always equal to double the number of octahedral voids in any crystal?

I came accross the question whether the number of tetrahedal voids is always equal to twice the number of octahedral voids (in the case where both the voids are present). The key was given as the ...
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24 views

Is the alloy of Fe, Si substitution alloy or interstitial alloy?

When atoms of the solute in a solid solution occupy positions normally occupied by a solvent atom, we have a substitutional alloy. When the sol- ute atoms occupy interstitial positions in the “holes” ...
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1answer
247 views

Melting point of crystalline solids

Why crystalline solids have sharp melting points but melting point of amorphous solids vary within a range? Is it because the interaction energy is equal between atoms of crystalline solids so they ...
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1answer
89 views

Why are crystalline solids anisotropic? [closed]

Why crystalline solids are anisotropic whereas amorphous solids are isotropic? Is it because in crystalline solids, X, Y and Z dimensions vary, but so does in amorphous. Please write as simple as ...
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1answer
213 views

Are clathrates and interstitial compounds the same thing?

In the book$\ce{^{[1]}}$, it's given that clathrates are compounds in which gases are entrapped within cavities of crystal lattices of certain organic or inorganic compounds. Interstitial compounds ...
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Unit cell in a hexagonal closed pack structure

My textbook says that there are only 14 possible 3D lattices(Bravais Lattices). One of these 14 lattices is a hexagonal lattice in which only a primitive variation is given to be possible. But then I ...
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1answer
87 views

Cation-anion radius ratio of manganese difluoride

How to determine the cation-anion radius ratio for $\ce{MnF2}?$ I tried to calculate the $r_\mathrm{c}/r_\mathrm{a}$ ratio using the relationships: $$2r_\mathrm{c} = c$$ and $$(2r_\mathrm{c} + 4r_\...
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28 views

Sphalerite type structure

There are binary diamond type structures for example S and Zn form sphalerite. I thought the reason this formed was because of the big difference in the radii of the atoms that allows the smaller atom ...
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1answer
66 views

Is there a crystal structure of ammonia in ionic form?

Like solid $\ce{PCl5}$, does solid $\ce{NH3}$ exist as $\ce{[NH4+][NH2-]}$ (i.e. ammonium amide)?
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92 views

Why is liquid germanium denser than solid germanium?

Why are some elements like Ge and Si have liquids denser than their solids? In water it is explainable by H bonding, but no H bonds or such are there in Ge and Si. Well, I want an explanation about ...
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1answer
169 views

Does a unit cell have to contain a whole number of atoms?

I was given this problem recently to compute the number of ions in a unit cell of ferrous oxide $\ce{FeO}$. The data given was: Side length $a = \pu{5 Å}$ Density $d = \pu{4 g/cc}$ Using the formula ...
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1answer
203 views

Why does Xenon Hexafluoride exist as [XeF5+][F-] and not [XeF5+][XeF2-] in the solid state [closed]

I already referred to this similar question but it yielded no explanation for the reason. Cations and anions of similar sizes stabilize each other through lattice energy effects in the solid state. ...
4
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1answer
107 views

Fractional index in a chemical formula of metal oxide

I have just read an article in which they used $\ce{WO3}$ and $\ce{WO_{2.9}}$ as precursors, whose objective was to form $\ce{WS2}$, in an atmosphere of argon by CVD. In one boat there is the powder ...
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93 views

Data-processing pipeline for protein x-ray crystallography: uncertain of terminology and order of procedures [closed]

Background: I am trying to get an overview of the data-processing pipeline for solving protein structures by x-ray crystallography, and in a very simple way understand what mathematical procedures are ...

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