Stopping and Range of Ions in Matter

Stopping and Range of Ions in Matter (SRIM) is a group of computer programs which calculate interaction of ions with matter

Stopping power (particle radiation)

In passing through matter, fast charged particles ionize the atoms or molecules which they encounter. Thus, the fast particles gradually lose energy in many small steps. Stopping power is defined as the average energy loss of the particle per unit path length, measured for example in MeV/cm...

; the core of SRIM is a program Transport of ions in matter (TRIM). The programs were developed by James F. Ziegler and Jochen P. Biersack around 1983 and are being continuously upgraded with the major changes occurring approximately every five years. SRIM is based on a Monte Carlo simulation method

Monte Carlo method

Monte Carlo methods are a class of computational algorithms that rely on repeated random sampling to compute their results. Monte Carlo methods are often used in computer simulations of physical and mathematical systems...

, namely the
binary collision approximation

Binary collision approximation

The binary collision approximation signifies a method used in ion irradiation physics to enable efficient computer simulation of the penetration depth and...

with a random selection of the impact parameter of the next colliding ion. As the input parameters, it needs the ion type and energy (in the range 10 eV - 2 GeV) and the material of one or several target layers. As the output, it lists or plots

the three-dimensional distribution of the ions in the solid and its parameters, such as penetration depth, its spread along the ion beam (called straggle) and perpendicular to it, all target atom cascades
Collision cascade
A collision cascade is a set of nearby adjacent energetic collisions of atoms induced by an energetic particle in a solid or liquid....

in the target are followed in detail;
concentration of vacancies, sputtering rate, ionization, and phonon production in the target material;
energy partitioning between the nuclear and electron losses, energy deposition rate;

The programs are made so they can be interrupted at any time, and then resumed later.
They have a very easy-to-use user interface and built-in default parameters for all ions and materials. Those features made SRIM immensely popular. However, it doesn't take account of the crystal structure nor dynamic composition changes in the material that severely limits its usefulness in some cases. Other approximation of the program include

binary collision (i.e. the influence of neighboring atoms is neglected);
recombination of knocked off atoms (interstitials) with the vacancies is neglected;
The electronic stopping power is an averaging fit to a large number of experiments
the interatomic potential as a universal form which is an averaging fit to quantum mechanical calculations
the target atom which reaches the surface can leave the surface (be sputtered
Sputtering
Sputtering is a process whereby atoms are ejected from a solid target material due to bombardment of the target by energetic particles. It is commonly used for thin-film deposition, etching and analytical techniques .-Physics of sputtering:...

) if it has momentum and energy to pass the surface barrier.
The system is layered, i.e. simulation of materials with composition differences in 2D or 3D is not possible.
The threshold displacement energy
Threshold displacement energy
The threshold displacement energy T_d is the minimum kinetic energythat an atom in a solid needs to be permanentlydisplaced from its lattice site to adefect position.It is also known as "displacement threshold energy" or just "displacement energy"....

is a step function for each element.

SRIM originated in 1983 as a DOS based program then called TRIM. The DOS version was upgraded until 1998 and is still available for download. It will run on a Unix PC having a DOS emulator. SRIM-2000 requires a computer with any Windows operating system. The program may work with Unix or Macintosh based systems through Wine

Wine (software)

Wine is a free software application that aims to allow computer programs written for Microsoft Windows to run on Unix-like operating systems. Wine also provides a software library, known as Winelib, against which developers can compile Windows applications to help port them to Unix-like...

See also