vacancy

(redirected from Job Vacancy)
Also found in: Dictionary, Thesaurus, Legal, Financial.

vacancy

Physics a defect in a crystalline solid caused by the absence of an atom, ion, or molecule from its position in the crystal lattice

Vacancy

 

(also Schottky defect), a crystal defect owing to the absence of an atom or ion at a crystal-lattice point. Vacancies exist in all crystals, however carefully the crystals are grown. In a real crystal, vacancies arise and vanish as a result of the atoms’ thermal motion. The mechanism of vacancy formation can be represented as the discharge of atoms of the surface layer onto the surface with the subsequent transfer of the surface “holes” developed. Here, in place of bonds with three neighboring atoms, only one bond remains and the other two are broken. Consequently, the work necessary to form a vacancy is equal to the energy of two bonds.

Vacancies migrate randomly in the crystal, changing places with neighboring atoms. The motion of a vacancy is the main cause of the intermixing (self-diffusion) of atoms in a crystal, as well as of the mutual diffusion of contacting crystals. A specific equilibrium concentration of vacancies corresponds to each temperature. The number of vacancies in metal crystals near the melting point reaches 1-2 percent of the number of atoms. For aluminum at room temperature, one vacancy occurs per 1012 atoms, and in metals such as silver and copper, the number of vacancies at room temperature is even smaller. However, despite the small concentration, vacancies substantially influence the physical properties of the crystal: for example, the density decreases and ionic conductance is produced. Vacancies play an important role in heat treatment processes, relaxation of metals, re-crystallization of metals, sintering, and other processes.

REFERENCES

Wert, C, and R. Thomson. Fizika tverdogo tela. Moscow, 1966. (Translated from English.)
Kitell, C. Vvedenie v fiziku tverdogo tela, 2nd ed. Moscow, 1963. (Translated from English.)

vacancy

[′vā·kən·sē]
(solid-state physics)
A defect in the form of an unoccupied lattice position in a crystal.
References in periodicals archive ?
The job vacancy rate (JVR) measures the proportion of total posts that are vacant, according to the definition of job vacancy above, expressed as a percentage of the number of job vacancies divided by the sum of the number of occupied posts plus the number of job vacancies all multiplied by 100.
In August of last year the job vacancy rate of real estate industry posted at 4.
There are over 10 dole claimants chasing every job vacancy in nearly a quarter of all local authorities.
Registered nurses (RNs) and caregivers are among the ten highest vacancy jobs in New Zealand, with RNs also falling into the highest vacancy high-skill jobs, according to the Department of Labour's job vacancy monitoring programme report for July.
10 /PRNewswire/ -- Despite the economic slowdown, there are still nearly 1,300 local manufacturing jobs open according to the Fall 2002 Job Vacancy Survey Report released today by the Center for Competitive Workforce Development (CCWD).
5 percent job vacancy rate, or 511 law-enforcement positions.
For every job vacancy, three candidates are short-listed and directed to the plant.
Called "Open Access", the system will give the unemployed quick access to job vacancy information.
The deployment of Lyrix has allowed the reuse of both images and text which were used extensively throughout the previous website in most sections including FAQs and job vacancy postings.
Taipei, June 25, 2012 (CENS)--Due to the global economic slowdown, the number of job vacancies in Taiwan decreased by 30,000 in February 2012 from a year earlier, causing the job vacancy to drop to 2.