AMTsolver - Angular Momentum Transfer Solver

Overview

AMTsolver is a C++ program that calculates the spectral angular momentum (dL/dω) transferred to a nanoparticle (NP) due to interaction with a fast-moving electron. The calculation is performed by analytically solving the closed surface integral, resulting in a double multipolar sum expression. The program focuses exclusively on the external field contribution and calculates the total angular momentum transfer (ΔL) for different values of the impact parameter b.

Features

• Computes frequency integrals using Gauss-Kronrod quadrature with adaptive partition
• Saves spectral results to dldw_*.dat files
• Saves integrated angular momentum results to DL_*.dat files
• Supports multiple parameter sets via CLI
• Automatic convergence checking with configurable threshold
• Parallel computation support (via OpenMP)

Prerequisites

• C++17 compatible compiler (g++ recommended)
• Boost libraries (version 1.70+)
• complex_bessel library
• CLI11 (for command line parsing)

Installation

bash git clone https://github.com/yourusername/AMTsolver.git cd AMTsolver mkdir build

Standard build

bash g++ -Iinclude -c src/IN51.cpp -o build/IN51.o g++ -Iinclude -Iinclude/Dielectric/DrudeAl -c src/main.cpp -o build/main.o -lcomplex_bessel g++ build/IN51.o build/main.o -o bin/AMTsolver -lcomplex_bessel

Parallel build (OpenMP)

bash g++ -fopenmp -O2 -std=c++17 -Iinclude -c src/main.cpp -o build/main.o -lcomplex_bessel g++ build/IN51.o build/main.o -o bin/AMTsolver -lcomplex_bessel -fopenmp ```

Basic Command (example)

bash ./AMTsolver -a <radius_nm> -b <impact_param_nm> -v <velocity>

Single Calculation

bash ./AMTsolver -a 50.0 -b 55.0 -v 0.7

Velocity Scan (20 points)

bash ./AMTsolver -a 50.0 -b 55.0 --vscan -n 20

Impact parameter scan

bash ./AMTsolver -a 50.0 -v 0.7 --bscan -n 30 -e 1e-5

Command Line Options

| Option | Description | Default Value | Constraints | |--------------|--------------------------------------------------|---------------|----------------------------------| | -a <float> | Nanoparticle radius (nm) | 1.0 | Must be > 0 | | -b <float> | Impact parameter (nm) | 1.5 | Must be > NP radius (-a) | | -v <float> | Electron velocity (fraction of c) | 0.7 | 0.0 ≤ v ≤ 0.999 | | --vscan | Enable velocity scan mode | false | Requires -n for point count | | --bscan | Enable impact parameter scan mode | false | Requires -n for point count | | --contour | Enable velocity vs. impact parameter contour | false | Combines --vscan and --bscan | | -e <float> | Convergence threshold | 1e-4 | Must be > 0 | | -n <int> | Number of points in scans | 9 | Must be ≥ 2 | | -m <int> | Minimum multipole order (ℓ) | 1 | Must be ≥ 1 |

Notes: - All numerical values must be positive - Scans generate data files in the output directory structure - Contour mode generates 2D parameter space analysis

Output structure

text results/ └── material=<material>/ └── a=<radius>nm/ └── <timestamp>/ ├── v_scan_for_b=<impact_param>nm/ # Velocity scans │ ├── Lmax=<value>/ │ │ ├── DLy_<params>.dat │ │ └── error_DLy_<params>.dat │ └── MultipolarConvergence/ │ └── MultipolarConvergence_<params>.dat ├── b_scan_for_v=<velocity>c/ # Impact param scans │ └── ... └── simulation_parameters.txt # Metadata

For citations

@software{AMTsolver, author = {Jorge Luis Briseño-Gómez}, title = {AMTsolver: Angular Momentum Transfer Calculator}, year = {2023}, publisher = {GitHub}, journal = {GitHub repository}, howpublished = {\url{https://github.com/LuisBrise/AMTsolver}}