ReCo.jl/graphics/CairoMakie_graphics/potential.jl

using CairoMakie
using LaTeXStrings: @L_str

include("../../visualization/common_CairoMakie.jl")

const minimum_r_σ_ratio = 2^(1 / 6)

function U_LJ_ϵ_ratio(r_σ_ratio::Real)
    σ_r_ratio⁶ = r_σ_ratio^(-6)
    return 4 * (σ_r_ratio⁶^2 - σ_r_ratio⁶)
end

function U_WCA_ϵ_ratio(r_σ_ratio::Real)
    if r_σ_ratio > minimum_r_σ_ratio
        return zero(r_σ_ratio)
    else
        return U_LJ_ϵ_ratio(r_σ_ratio) + 1
    end
end

function plot_potentials()
    init_cairomakie!()

    fig = gen_figure()

    max_x = 2.5

    max_y = 1.05
    min_y = -max_y

    ax = Axis(
        fig[1, 1]; xlabel=L"r / σ", ylabel=L"U(r) / ϵ", limits=(0.88, max_x, min_y, max_y)
    )

    r_σ_ratio = LinRange(0.95, max_x, 1000)

    LJ = lines!(ax, r_σ_ratio, U_LJ_ϵ_ratio.(r_σ_ratio))

    WCA = lines!(ax, r_σ_ratio, U_WCA_ϵ_ratio.(r_σ_ratio))

    minimum_r_σ_ratio_line = lines!(
        ax,
        [minimum_r_σ_ratio, minimum_r_σ_ratio],
        [min_y, max_y];
        linestyle=:dash,
        linewidth=1,
    )

    Legend(
        fig[1, 2],
        [LJ, WCA, minimum_r_σ_ratio_line],
        [L"U_{LJ}", L"U_{WCA}", L"\frac{r}{σ} = 2^{1/6}"],
    )

    set_gaps!(fig)

    save_fig("potential.pdf", fig)

    return nothing
end