Resolving the structure of TiBe₁₂

There has been considerable controversy regarding the structure of TiBe₁₂, which is variously reported as hexagonal and tetragonal. Lattice dynamics simulations based on density functional theory (DFT) show the tetragonal phase space group I4/mmm to be more stable over all temperatures, while the hexagonal phase exhibits an imaginary phonon mode, which, if followed, would lead to the cell adopting the tetragonal structure. We then report the predicted ground state elastic constants and temperature dependence of the bulk modulus and thermal expansion for the tetragonal phase.

Computing details

Beryllium titanium (12/1)

Crystal data

Be12Ti	c = 4.1641 Å
Tetragonal, I4/mmm	V = 225.52 Å^3
a = 7.3592 Å	Z = 2

Data collection

h = →	l = →
k = →

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Biso*/Beq
Be1	0.25000	0.25000	0.25000
Be9	0.35146	0.00000	0.00000
Be17	0.28252	0.50000	0.00000
Ti1	0.00000	0.00000	0.00000