fun_G01_cross_section.f90

直接用途

fun_G01_cross_section 在截面表上按能量做线性插值，并对表外能量使用边界值。

参数表

参数	方向	shape/范围	含义与局部约定
`energy`	in	scalar or caller-provided array	用于查询截面的粒子能量。
`Nmax`	in	scalar or caller-provided array	截面表最大点数。
`cross_section`	in	`(1:2,1:Nmax)`	截面表；第一行通常为能量，第二行为截面值。

返回值

Interpolated or boundary-clamped cross-section value.

局部假设

碰撞例程假定粒子数组 par(1:6,...) 中 1:3 是位置、4:6 是速度。随机数来自 Fortran random_number；能量、截面、密度和时间步单位必须由调用方保持自洽。这里不替调用方设置随机种子。

实现逻辑

实现假定截面表能量点等间距，先由能量定位区间，再做线性插值；表外能量钳制到端点。

调用注意

本页只说明该例程本身的调用边界和实现事实；完整接口声明和源码级 API 仍以英文侧的 generated API 为准。

Direct Purpose

fun_G01_cross_section interpolate a tabulated collision cross section.

Parameter Table

Parameter	Direction	Shape/range	Meaning and local convention
`energy`	in	scalar or caller-provided array	Particle energy at which the cross section is evaluated.
`Nmax`	in	scalar or caller-provided array	Number of tabulated energy points.
`cross_section`	in	`(1:2,1:Nmax)`	Tabulated data `(1:2,1:Nmax)`. Row 1 stores energy values and row 2 stores cross-section values.

Return Value

Interpolated or boundary-clamped cross-section value.

Local Assumptions

Collision routines assume par(1:6,...) stores position in 1:3 and velocity in 4:6. Random numbers come from Fortran random_number. Units of energy, cross section, density, and time step must be kept self-consistent by the caller. These routines do not seed the RNG.

Implementation Notes

The implementation assumes uniformly spaced tabulated energies, locates the energy interval, then applies linear interpolation; out-of-range energies are clamped to endpoints.

Generated API

The generated Doxygen record for this Fortran function is represented by the source-backed parameter and return tables above. Rendering this function signature directly through Breathe currently emits a parser warning, so the warning-free page keeps the manual API table as the canonical rendered form.