| \(\mathbf R_n\), \(\mathbf R_i\), \(\mathbf R\) |
Direct-lattice or nuclear/ionic position vector |
| \(\mathbf r_j\), \(\mathbf r_\mu\), \(\mathbf r_{n\mu}\) |
Electron or basis-atom position |
| \(\mathbf a_i\) |
Primitive direct-lattice vector |
| \(\mathbf b_i\) |
Primitive reciprocal-lattice vector |
| \(V_{\mathrm c}\), \(V_{\mathrm{WS}}\) |
Primitive-cell volume |
| \(V\) |
Sample/crystal volume |
| \(A\) |
Area or scattering amplitude, depending on context |
| \(L\) |
Sample length |
| \(d_{hkl}\) |
Interplanar spacing |
| \(d\) |
Characteristic sample diameter or boundary length |
| \(\mathbf G\) |
Reciprocal-lattice vector |
| \(\mathbf k\), \(\mathbf k'\) |
Incident/scattered wave vector |
| \(\Delta\mathbf k\) |
Scattering vector \(\mathbf k'-\mathbf k\) |
| \(\mathbf q\) |
Phonon wave vector |
| \(q\) |
Magnitude/scalar component of \(\mathbf q\) |
| \(q_D\) |
Debye wave vector |
| \(\Omega_{\mathrm{BZ}}\) |
First-Brillouin-zone volume |
| \(h,k,l\) |
Miller/reciprocal-lattice indices |
| \((hkl)\) |
Family of lattice planes |
| \(n_{\mathrm B}\) |
Bragg diffraction order |
| \(r'\) |
Number of atoms in the primitive cell/basis |
| \(N\) |
Number of primitive cells, illuminated cells, or electrons |
| \(N_i\) |
Number of cells/modes along direction or propagating modes |
| \(M_k\), \(M_\alpha\), \(M\) |
Nuclear/atomic mass |
| \(m_{\mathrm e}\) |
Electron mass |
| \(m_{\mathrm s}\) |
Sample mass |
| \(\mu\) |
Reduced mass, absorption coefficient, or chemical potential |
| \(Z_k\) |
Nuclear charge number |
| \(-e\) |
Electron charge |
| \(H\), \(H_a\) |
Hamiltonian / adiabatic Hamiltonian |
| \(\Psi\), \(\psi_s\), \(\chi_s\) |
Full, electronic, and nuclear wavefunctions/amplitudes |
| \(U\) |
Internal energy or lattice potential energy |
| \(U_{\mathrm{eq}}\) |
Static equilibrium lattice energy |
| \(U_{\mathrm{harm}}\), \(U_{\mathrm{anh}}\) |
Harmonic/anharmonic potential-energy contributions |
| \(U_0\) |
Zero-point vibrational energy |
| \(U_{\mathrm{th}}\) |
Thermal vibrational internal energy |
| \(E\), \(E_F\) |
Single-electron energy; Fermi energy |
| \(E_{\mathrm{coh}}\) |
Cohesive energy |
| \(E_{12}\) |
Two-level-system energy splitting |
| \(F\) |
Force or Helmholtz free energy, context-dependent |
| \(S(\mathbf K)\), \(S_{\mathbf G}\) |
Structure factor |
| \(S\) |
Thermopower / Seebeck coefficient |
| \(T\) |
Absolute temperature |
| \(\Theta_D\), \(\Theta_E\) |
Debye and Einstein temperatures |
| \(T_F\) |
Fermi temperature |
| \(T^\ast\) |
Crossover temperature |
| \(\beta\) |
Inverse thermal energy |
| \(k_B\) |
Boltzmann constant |
| \(\hbar\), \(h\) |
Reduced Planck constant; Planck constant |
| \(N_A\) |
Avogadro constant |
| \(R\) |
Gas constant |
| \(\nu\) |
Amount of substance |
| \(C\) |
Heat capacity of a sample |
| \(C_V\) |
Heat capacity at constant volume |
| \(C_p\) |
Heat capacity at constant pressure |
| \(c_m\) |
Molar heat capacity |
| \(c_{\mathrm{mass}}\) |
Heat capacity per mass |
| \(c_{\mathrm{vol}}\), \(c_V\) |
Heat capacity per volume |
| \(c_{V,r}(q)\) |
Modal contribution to \(c_V\) |
| \(p\) |
Pressure |
| \(B\) |
Bulk modulus |
| \(\alpha_L\), \(\alpha_V\) |
Linear and volume thermal expansion coefficients |
| \(\kappa\) |
Thermal conductivity |
| \(\boldsymbol\kappa\) |
Thermal-conductivity tensor |
| \(\rho\) |
Density field or electrical resistivity |
| \(\sigma\) |
Electrical conductivity or scattering cross section |
| \(\omega\) |
Angular frequency |
| \(\omega_0\), \(\omega_E\), \(\omega_D\) |
Local, Einstein, and Debye angular frequencies |
| \(\omega_{\mathbf q r}\) |
Angular frequency of phonon mode \((\mathbf q,r)\) |
| \(\omega_r(\mathbf q)\) |
Functional form of phonon branch \(r\) |
| \(D(\omega)\) |
Phonon density of states in frequency space |
| \(D(E)\) |
Electronic density of states |
| \(D_{\alpha i}^{\beta j}(\mathbf q)\), \(D(\mathbf q)\) |
Dynamical matrix |
| \(\Phi_p\), \(\Phi_1\) |
Plane-plane force constants |
| \(K_{\mathrm{bond}}\) |
Local bond stiffness |
| \(f\), \(f_j\) |
Force constant in two-atom chain; atomic form factor |
| \(\mathbf u\), \(u_n\), \(u_{n\alpha i}\) |
Atomic displacement field/components |
| \(A_{\alpha i}(\mathbf q)\) |
Polarization amplitude |
| \(r\) |
Phonon branch/polarization index |
| \(n\), \(\langle n\rangle\), \(\langle n_{\mathbf q r}\rangle\) |
Quantum number / phonon occupation |
| \(f(E)\) |
Fermi-Dirac occupation probability |
| \(v_g\), \(v_s\), \(v_i\), \(v_L\), \(v_T\), \(v_F\) |
Group, sound, branch, longitudinal, transverse, and Fermi velocities |
| \(\tau\) |
Relaxation time / phonon lifetime |
| \(\ell\) |
Mean free path |
| \(\lambda\), \(\lambda_{\mathrm{th}}\) |
Radiation wavelength; thermal phonon wavelength |
| \(\mathbf J_h\), \(J_{h,x}\) |
Heat-current density and component |
| \(\mathbf J_{\mathrm e}\) |
Electrical current density |
| \(\mathbf E\) |
Electric field |
| \(\varphi_{\mathrm{el}}\) |
Electric potential |
| \(\gamma_{\mathbf q r}\), \(\gamma\) |
Mode and averaged Grüneisen parameter |
| \(\gamma\) |
Sommerfeld coefficient |
| \(L_0\) |
Lorenz number |
| \(\mathrm{RRR}\) |
Residual resistance ratio |