Muffin-tin approximation Muffin-tin approximation The muffin-tin approximation is a shape approximation of the potential well in an crystal lattice. It is most commonly employed in quantum mechanical simulations of the electronic band structure in solids. The approximation was proposed by John C. Slater. Augmented plane wave method (APW) is a method which uses muffin-tin approximation. It is a method to approximate the energy states of an electron in a crystal lattice. The basic approximation lies in the potential in which the potential is assumed to be spherically symmetric in the muffin-tin region and constant in the interstitial region. Wave functions (the augmented
Wedding anniversary at the Chicago Public Library. Wedding anniversary A wedding anniversary is the anniversary of the date a wedding took place. Traditional names exist for some of them: for instance, fifty years of marriage is called a "golden wedding anniversary" or simply a "golden anniversary" or "golden wedding". The historic origins of wedding anniversaries date back to the Holy Roman Empire, when husbands crowned their wives with a silver wreath on their twenty-fifth anniversary, and a gold wreath on the fiftieth. Later, principally in the twentieth century, commercialism led to the addition of more anniversaries being represented by a named gift.