MCNP models all of its physics using data drawn from nuclide specific
data tables that must be provided to it.
These tables provided partial and total interaction cross sections as a
function of neutron energy, the energy-angle spectrum of the emergent
neutrons, and other interaction data.
There is a wide choice of tables that can be provided to MCNP depending
on the nature of the problem that is to be solved, and upon the accuracy
that is desirable in the results.
The best tables are continuous energy evaluations, and SNOMAN shall make
use of these.
The data tables typically cover neutron interactions in the energy range
from
MeV.
For some nuclides in a limited set of materials, such as 
H in light
water and 
H in heavy water, thermal tables are available.
These tables describe the behaviour of the neutron when its energy is
comparable to the temperature of the medium through which it is moving.
A thermal table provides replacement tables for both the elastic and
inelastic cross sections and the energy-angle spectrum of the neutron
emergent from a scattering incident.
A thermal table is provided for use at a particular temperature.
All the thermal data tables used in SNOMAN are intended for use at or near
K.
Tables are provided for the following elements/isotopes:
H, H, 
He, 
He, 
B, 
B, C, 
N,
N, 
O, 
O, 
F, 
Na, Mg, 
Al, Si, S,
S, Cl, Ar, K, Ca, 
Cr, 
Cr, 
Cr, 
Cr,
Mn, Fe, 
Fe, 
Fe, 
Fe, Ni, 
Ni,
Ni, 
Ni, 
Ni, 
Cu, 
Cu, 
I, 
I,
Cs ,
Cs, 
Cs, 
Cs, 
Cs, 
Ba,
Pb, 
Pb and 
Pb.
Thermal tables exist for use with H or H in light and heavy water.
These are used in preference to the standard tables at neutron energies below
about 
eV.
The use of these tables is essential for the correct simulation of neutron
transport in light or heavy water.
These thermal tables take atomic effects into account when they are used to
simulate neutron transport at thermal energies.