• Blog Stats

    • 75,067 hits
  • Archives

  • Enter your email address to subscribe to this blog and receive notifications of new posts by email.

    Join 156 other followers

  • Copyright notice

    This blog entry and all other text on this blog is copyrighted, you are free to read it, discuss it with friends, co-workers and anyone else who will pay attention.

    If you want to cite this blog article or quote from it in a not for profit website or blog then please feel free to do so as long as you provide a link back to this blog article.

    If as a school teacher or university teacher you wish to use content from my blog for the education of students then you may do so as long as the teaching materials produced from my blogged writings are not distributed for profit to others. Also at University level I ask that you provide a link to my blog to the students.

    If you want to quote from this blog in an academic paper published in an academic journal then please contact me before you submit your paper to enable us to discuss the matter.

    If you wish to reuse my text in a way where you will be making a profit (however small) please contact me before you do so, and we can discuss the licensing of the content.

    If you want to contact me then please do so by e-mailing me at Chalmers University of Technology, I am quite easy to find there as I am the only person with the surname “foreman” working at Chalmers. An alternative method of contacting me is to leave a comment on a blog article. If you do not know which one to comment on then just pick one at random, please include your email in the comment so I can contact you.

Reckless use of pesticides

Dear Reader,

It has come to my attention that a person in the USA caused the deaths of four members of his family when he attempted to use a restricted pesticide to kill bugs at his home in Texas. What this man did was to use a product which is not intended to be sold to or used by the general public. In the UK the use of this chemical is strongly limited to professional users who have to undergo special training before they use it.

It was aluminium phosphide, this is one of the more dangerous pesticides which is in current use. It is a solid which on contact with water (or acids) will generate phosphine gas. The take home message is if you face a pest control job which you can not solve using over the counter products sold to the general public then unless you have the special training (and equipment) required to use a professional use only product then leave work with such a product to a professional (and I hope competent) pest control worker.

You might wounder what aluminium phosphide is, it is AlP, it is a solid with the same crystal strucutre as zinc sulfide (zincblende). Here the aluminium and phosphrous atoms have tetrahedral coordination environments. This is a compound with a cubic cell (a = 5.451 Å). The fractional coordinates of the atoms are

Al 0, 0, 0

Al ½ ½ 0

Al ½ 0 ½

Al 0 ½ ½

P ¼ ¼ ¼

P ¾ ¾ ¼

P ¼ ¾ ¾

P ¾ ¼ ¾

We can make a xyz file for a single unit cell.

18
XYZ file : Unit cell AlP
Al 0 0 0
Al 5,451 0 0
Al 0 5,451 0
Al 5,451 5,451 0
Al 0 0 5,451
Al 5,451 0 5,451
Al 0 5,451 5,451
Al 5,451 5,451 5,451
Al 2,7255 2,7255 0
Al 2,7255 2,7255 5,451
Al 2,7255 0 2,7255
Al 2,7255 5,451 2,7255
Al 0 2,7255 2,7255
Al 5,451 2,7255 2,7255
P 1,36275 1,36275 1,36275
P 4,08825 4,08825 1,36275
P 1,36275 4,08825 4,08825
P 4,08825 1,36275 4,08825

Here are three views of the unit cell for you to look at

alpview1

alpview2

alpview3

It should be clear that the empirical formula of the compound is AlP. We have eight aluminiums at the corners of the cell, each is shared equally between eight cells, we also have six aluminiums on the faces. Each of these six aluminiums is shared between two cells. This gives us a total of four aluminiums.

We have four phosphorus atoms (in a fetching orange) which are totally inside the unit cell. Thus we have a 1:1 ratio of aluminium to phosphorus atoms.

 

Advertisements

Go on, Have your say !

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: