CHEM-002 Lecture Notes - Lecture 24: Intensive And Extensive Properties, Face Diagonal, Space Diagonal

49 views2 pages

chocolatedeer31

22 Apr 2017

School

Georgetown University

Department

Chemistry

Course

CHEM-002

Professor

Dedios Angel

For unlimited access to Class Notes, a Class+ subscription is required.

Document Summary

The concentrations are all divided by 1m and the pressures are all divided by 1atm. What you actually get is the ratio of each of these correspond to 1atm, so tall of these are dimensionless. Anything inside the logortithm function must be dimensionless. We"(cid:396)e goi(cid:374)g to look at (cid:272)(cid:396)(cid:455)stals a(cid:374)d (cid:272)o(cid:374)(cid:272)e(cid:374)t(cid:396)ate o(cid:374) those that a(cid:272)tuall(cid:455) (cid:271)elo(cid:374)g to the (cid:272)u(cid:271)i(cid:272) system this is actually pretty few of them. The crystal structure is a combination of the lattice (a combination of points) and a motif (basis). Three-dimensional lattice the(cid:396)e is a u(cid:374)it that (cid:455)ou (cid:272)ould (cid:862)(cid:272)ut out(cid:863) that (cid:455)ou (cid:272)ould (cid:396)epli(cid:272)ate to reproduce the entire crystal structure. These can be defined by a series of vectors. We"(cid:396)e just goi(cid:374)g to stud(cid:455) the cu(cid:271)i(cid:272) e(cid:454)a(cid:373), (cid:449)hi(cid:272)h has a u(cid:374)it (cid:272)ell (cid:449)ith e(cid:395)ual edges. Most elements, but not most cystals, are cupic. Primitive one lattice point per unit cell (cid:862)si(cid:373)ple(cid:863) o(cid:396) (cid:862)p(cid:396)i(cid:373)iti(cid:448)e(cid:863) Non primate more than one lattice point per unit cell.

Related Questions

I need help answering pages 104-106

103 UNIT CELL GEOMETRY INTRODUCTION These cells are Most solids form crystal lattices composed of repeating box-like units (unit cells). These ce parallelepipeds whose shape is determined by the lengths of the edges of the parallelepipeds an between the edges. A cubic cell has 90Â° angles between all of its neighboring edges and all of its edge are equal to each other There are three possible arrangements of atoms within a cubic cell. In a simple cubic unit, there is an located at each corner of the cube (and each corner atom is shared by seven other ce atoms present in a simple cubic unit cell. Corner atoms touch each other (exce atom ere are no other pt in the diagonal direction) In a body-centered cubic unit, there are corner atoms (as in the simple cube), but, in addition atom completely within the body of the cube that is not shared with any other cell. In the body-centered eu cell, none of the corner atoms touch each other but they all touch the central atom bic In a face-centered cubic unit, there a there is an atom centered on each of the six faces of the cell. Half of a face-centered atom belongs to re, again, corner atoms shared with the surrounding cells. In addition, toms, The other half belongs to the cell adjacent to that face. Each face-centered atom touches its four corner a but the corner atoms do not touch each other PROCEDURE The class should divide into eight groups and each group will check out a cubic cell model kit. Each kit 1. should contain: 8-1/8 spheres; 6-1/2 spheres; 1 - whole sphere; metal connecting rods Consult the diagrams in your textbook and build a simple cubic unit cell. Collaborate with the seven other 2. 3. 4. 5. groups of students and assemble a model of a portion of a solid formed from eight simple cubic unit cells Draw a diagram of a simple cubic unit cell and answer the questions on the report sheet for this cell type Repeat steps 2 and 3 for the body-centered and face-centered cubic units Observe your profess or's demonstration of a hexagonal unit cell and answer the questions on the report sheet.

1. Grain Boundaries

A material composed of only one crystal is called a single crystal, a material which consists of two crystals is called

a bi-crystal, while a material composed of many grains is referred to as being polycrystalline. We described

a low angle, tilt grain boundary as being one which was composed of a series of edge dislocations spaced along the

plane of intersection between the two grains (crystals). In this exercise, you will investigate the relationship between

the magnitude of the tilt angle between the two grains, and the spacing between the edge dislocations along the

grain boundary. In the Picture file, you will find a slide with pairs of grains which have been tilted by 2Â°, 4Â°, or 6Â° from one another. Each square represents a cubic unit

cell and the axis of rotation is vertical, out of the page.

(a) For each pair of grains, move the grains so that they just overlap at the top of the drawing. You do NOT

need to perform any additional rotation of the grains. Print a copy of your slide for this step.

(b) A darker grey region should form in your image where the two crystal overlap. For each pair of grains,

remove unit cells from the left grain to eliminate the regions of overlap between the two crystals. It is Ok

to have some white regions between the two grains as the atoms adjacent to the white area will shift their

atomic positions to better accommodate the void. In general there will be much more open volume along

the grain boundary than in the unaffected region of the grain. Print a copy of your slide for this step.

(d) For each grain boundary, determine the spacing between edge dislocations, D, in terms of the lattice

parameter, a. Print a copy of your slide for steps (c) and (d).

(e) Circle the correct answer that completes the sentence below.

The spacing between edge dislocations, D, _______________ the tilt angle of the grain boundary.

(i) is independent of

(ii) is inversely proportional to

(iii) has a linear relationship with

(iv) has a quadratic relationship with

(f) Circle the correct answer that completes the sentence below.

A tilt grain boundary is one where the axis of rotation of the grains is _____________ the plane of the grain

boundary.

(i) parallel to

(ii) perpendicular to

(iii) is canted out of the plane by an angle ï¹ 90ï° from

(g) On your drawing of the 2ï° tilt boundary, draw a Burgerâs circuit around a perfect region of the crystal AND

around an edge dislocation. Clearly mark the start and end positions of your Burgerâs circuit AND identify

the Burgerâs vector, B as the vector pointing from the end to the start of the Burgerâs circuit. Print a copy

of your slide for this step.

Note: Twist grain boundaries are related to screw dislocations in a similar manner, but the pictures are much

more difficult to draw.

The right grain in each pair is an image, and it is the bottom object in the stack. The left grain has unit cells which are grouped but you can still manipulate/erase individual unit cells. It might be a bit tedious to erase many unit cells.

Can someone explain the concepts of 3-12?

3- the boiling point if its nonpolar then the highest in mass, the stronger they are (if the are nonpolar). If they are polar then the smaller the radius and the larger charger the higher the boiling point. (if there is any information to add, please do so).

4- The Clasius Clapeyron equation is used, correct? If so, the equation would be ln(p2/1atm) = -38.56/8.314 x (1/348 - 1/351). For some reason though I am getting .99 at rather than .89

5- For enthlapy of Fusion is q = Enthlapy x moles. Because it is released, then it is exothermic which is negative. So 11.8/10 and being exothermic -1.18

6 and 7 I understand that. No need to explain

8- What equation is to calculate the lattice?

9 - Can you explain how the answer was picked? The options are not there but out of those options, it was (a) AI

10- For the band gap, the lower it goes down the periodic table, the lower the band gap (correct?)

11 - For this problem I have no idea which equation to use and I do not understand the problem.

12 - Same with this question as well.

CHEM-002 Lecture Notes - Lecture 24: Intensive And Extensive Properties, Face Diagonal, Space Diagonal

Document Summary

Get access

Related textbook solutions

Chemistry: Structure and Properties

Basic Chemistry

Principles of Chemistry Molecular Approach

Principles of Chemistry Molecular Approach

Chemistry: Structure and Properties

Chemistry: A Molecular Approach

Chemistry: A Molecular Approach

Principles of Chemistry: A Molecular Approach

Chemistry: The Central Science

Related Documents

CHEM-002 Lecture Notes - Lecture 25: Electrolytic Cell, Galvanic Cell, Space Diagonal

NSCI 1322 Lecture Notes - Lecture 70: Cubic Crystal System, Liquid Crystal, Metal

CHMA10H3 Lecture Notes - Lecture 14: Cubic Crystal System, Coordination Number

Related Questions