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Bravais Lattice

Bravais Lattices in 3D Figure 1. Primitive (red), conventional (blue if any) and Wigner-seitz cell (green) of 14 three-dimensional (3D) Bravais lattices. G...

Brillouin Zone Integration: Linear Tetrahedron Method

Introduction The translational symmetry of solids resulits in a quantum number, i.e. the crystal momentum $\mathbf{k}$. Consequently many quantities of the crystal, e.g. total energy and density...

Phonopy: Rutile TiO2

Phonon Dispersion of Rutile TiO$_2$ This is a summary of my using Phonopy to calculate phonon spectrum of rutile TiO$_2$. 1 Computational Details Below is a list of used packages and computation...

Matplotlib: 1D Chain ARPES Signal

ARPES Signal of 1D Chain within Tight-binding 1 The eigenvalues of 1D mono-atomic chain within the tight-binding model \[\begin{equation*} \varepsilon_\kappa = \varepsilon_0 - 2t\cos(\f...

Peierls Transition

Peierls Transition A Peierls transition or Peierls distortion is a distortion of the periodic lattice of a one-dimensional crystal. Atomic positions oscillate, so that the perfect order of the 1D ...

Matplotlib: Hydrogen Wave Function

Hydrogen Wave Function The normalized hydrogen wave function1 [\begin{equation} \label{eq:hydro_wfc} \psi_{nlm}(r,\theta,\phi) = \sqrt{ \left(\frac{2}{na_0}\right)^3\, \fr...

Matplotlib: Plot within a hexagon

Problem Suppose we have a periodic function $f(x,y)$ defined within a hexagonal unit cell, how can we plot the function on the Wigner-Seitz cell? Codes #!/usr/bin/env python # -*- coding: utf-8 ...

Fourier Transform of Radial Functions

Description of the problem Suppose we have a function which can be expressed in terms of spherical harmonics [\begin{equation} \label{eq:radial_fun} f(r, \theta, \phi) = \sum_{l=0...

Numerov Algorithm

Numerov’s method Numerov’s method1 (also called Cowell’s method) is a numerical method to solve ordinary differential equations of second order in which the first-order term does not appear. It is...

Plotly: Spherical Harmonics

Introduction In mathematics and physical science, spherical harmonics are special functions defined on the surface of a sphere. The spherical harmonics form a complete set of orthogonal functions...