physics-databases

# Physics Databases ## Overview Access physical constants and reference data from authoritative databases. Never hardcode physical constants — always query from `scipy.constants` (CODATA 2018) or NIST APIs. ## CRITICAL: Always Use Database Values - NEVER type physical constants from memory - ALWAYS use `scipy.constants` or NIST lookup - Constants change between CODATA editions (e.g., 2014 → 2018 → 2022) ## Core Workflows ### 1. CODATA Physical Constants (scipy.constants) ```python from scipy import constants as const # Fundamental constants print("=== Fundamental Constants (CODATA 2018) ===") print(f"Speed of light: c = {const.c:.10e} m/s") print(f"Planck constant: h = {const.h:.10e} J·s") print(f"Reduced Planck: ℏ = {const.hbar:.10e} J·s") print(f"Boltzmann constant: k = {const.k:.10e} J/K") print(f"Gravitational const: G = {const.G:.10e} m³/(kg·s²)") print(f"Elementary charge: e = {const.e:.10e} C") print(f"Electron mass: mₑ = {const.m_e:.10e} kg") print(f"Proton mass: mₚ = {const.m_p:.10e} kg") print(f"Neutron mass: mₙ = {const.m_n:.10e} kg") print(f"Vacuum permittivity: ε₀ = {const.epsilon_0:.10e} F/m") print(f"Vacuum permeability: μ₀ = {const.mu_0:.10e} H/m") print(f"Avogadro number: Nₐ = {const.N_A:.10e} mol⁻¹") print(f"Gas constant: R = {const.R:.10e} J/(mol·K)") print(f"Stefan-Boltzmann: σ = {const.sigma:.10e} W/(m²·K⁴)") print(f"Fine structure: α = {const.fine_structure:.10e}") print(f"Rydberg constant: R∞ = {const.Rydberg:.10e} m⁻¹") print(f"Bohr radius: a₀ = {const.physical_constants['Bohr radius'][0]:.10e} m") print(f"Standard gravity: g = {const.g:.6f} m/s²") print(f"Standard atmosphere: atm= {const.atm:.2f} Pa") ``` ### 2. Unit Conversions ```python # Energy conversions print("\n=== Energy Conversions ===") print(f"1 eV = {const.eV:.10e} J") print(f"1 cal = {const.calorie:.6f} J") print(f"1 BTU = {const.Btu:.6f} J") print(f"1 erg = {const.erg:.10e} J") # Length conversions print("\n=== Length Conversions ===") print(f"1 Å = {const.angstrom:.10e} m") print(f"1 au = {const.au:.6e} m") # astronomical unit print(f"1 ly = {const.light_year:.6e} m") print(f"1 pc = {const.parsec:.6e} m") # Temperature print(f"\n0°C = {const.zero_Celsius:.2f} K") # Pressure print(f"\n1 atm = {const.atm:.2f} Pa") print(f"1 bar = {const.bar:.2f} Pa") print(f"1 torr = {const.torr:.6f} Pa") ``` ### 3. Look Up Any CODATA Constant ```python # Search by name def find_constant(keyword): """Search CODATA constants by keyword.""" results = [] for name, (value, unit, uncertainty) in const.physical_constants.items(): if keyword.lower() in name.lower(): results.append((name, value, unit, uncertainty)) print(f" {name}") print(f" = {value:.10e} {unit}") print(f" ± {uncertainty:.4e}") return results print("Searching for 'Bohr':") find_constant("Bohr") print("\nSearching for 'magnetic moment':") find_constant("magnetic moment") ``` ### 4. Materials Project API ```python # pip install mp-api # Requires API key: https://materialsproject.org/api def query_materials_project(formula, api_key=None): """ Query Materials Project for material properties. Set MP_API_KEY environment variable or pass api_key. """ try: from mp_api.client import MPRester import os key = api_key or os.environ.get('MP_API_KEY') if not key: print("Set MP_API_KEY environment variable") return None with MPRester(key) as mpr: docs = mpr.summary.search(formula=[formula]) for doc in docs[:5]: print(f" {doc.material_id}: {doc.formula_pretty}") print(f" Space group: {doc.symmetry.symbol}") print(f" Energy above hull: {doc.energy_above_hull:.4f} eV/atom") print(f" Band gap: {doc.band_gap:.3f} eV") print(f" Density: {doc.density:.3f} g/cm³") return docs except ImportError: print("Install mp-api: pip install mp-api") return None # Example: query_materials_project("Si") ``` ### 5. Particle Data Group (PDG) ```python # Key particle properties (from PDG 2024) # These are reference values — for precision work, check pdg.lbl.gov particles = { 'electron': { 'mass_MeV': 0.51099895, 'charge': -1, 'spin': 0.5, 'lifetime': 'stable', }, 'proton': { 'mass_MeV': 938.27208816, 'charge': +1, 'spin': 0.5, 'lifetime': 'stable (> 10^34 years)', }, 'neutron': { 'mass_MeV': 939.56542052, 'charge': 0, 'spin': 0.5, 'lifetime_s': 878.4, # ~14.6 minutes }, 'muon': { 'mass_MeV': 105.6583755, 'charge': -1, 'spin': 0.5, 'lifetime_s': 2.1969811e-6, }, 'pion_charged': { 'mass_MeV': 139.57039, 'charge': +1, 'spin': 0, 'lifetime_s': 2.6033e-8, }, 'W_boson': { 'mass_GeV': 80.3692, 'charge': +1, 'spin': 1, }, 'Z_boson': { 'mass_GeV': 91.1876, 'charge': 0, 'spin': 1, }, 'Higgs': { 'mass_GeV': 125.20, 'charge': 0, 'spin': 0, }, } # Always cite: "Particle Data Group, Phys. Rev. D 110, 030001 (2024)" # For precision values: https://pdg.lbl.gov ``` ### 6. Astronomical Constants ```python # Solar system data (IAU 2015 values) print("\n=== Astronomical Constants ===") print(f"Solar mass: M☉ = 1.98892e30 kg") print(f"Solar radius: R☉ = 6.9634e8 m") print(f"Solar luminosity: L☉ = 3.828e26 W") print(f"Earth mass: M⊕ = 5.9722e24 kg") print(f"Earth radius: R⊕ = 6.3781e6 m") print(f"Moon mass: M☾ = 7.342e22 kg") print(f"AU: 1 AU = {const.au:.6e} m") # For precise values, use astropy: # from astropy import constants as astro_const # print(astro_const.M_sun) ``` ## Quick Reference | Constant | Symbol | Value | scipy.constants | |---|---|---|---| | Speed of light | c | 2.998×10⁸ m/s | `const.c` | | Planck | h | 6.626×10⁻³⁴ J·s | `const.h` | | Boltzmann | k_B | 1.381×10⁻²³ J/K | `const.k` | | Gravitational | G | 6.674×10⁻¹¹ m³/(kg·s²) | `const.G` | | Elementary charge | e | 1.602×10⁻¹⁹ C | `const.e` | | Electron mass | m_e | 9.109×10⁻³¹ kg | `const.m_e` | | Proton mass | m_p | 1.673×10⁻²⁷ kg | `const.m_p` | | Avogadro | N_A | 6.022×10²³ mol⁻¹ | `const.N_A` | | Gas constant | R | 8.314 J/(mol·K) | `const.R` | | 1 eV | — | 1.602×10⁻¹⁹ J | `const.eV` | | 1 Å | — | 1.0×10⁻¹⁰ m | `const.angstrom` | ## Tips 1. **Always `from scipy import constants as const`** — never type values manually 2. **Check units**: `const.physical_constants['Bohr radius']` returns (value, unit, uncertainty) 3. **For astrophysics**: use `astropy.constants` for additional astronomical constants 4. **For materials**: use `mp-api` to query the Materials Project database 5. **Cite your source**: "CODATA 2018 via scipy.constants" or "PDG 2024"