  Lattice Parameter is an important material feature in High Entropy Alloy
(HEA) Design. Vegards Law is typically used to estimate lattice parameters but
is often inaccurate for metal alloys due to an inability to account for charge
transfer which can affect atomic volumes. The present study used ab initio
simulation to calculate bond lengths between atoms of dissimilar elements in B2
intermetallic compounds which was then combined with a bond counting model to
produce a model to estimate the lattice parameters of Refractory BCC HEAS. The
model was tested using a supercell method which modeled various random solid
solution HEAs. The proposed model produced lattice parameters with superior
accuracy to Vegards Law without the need for large DFT calculations or fitting
parameters. The proposed model had a root mean squared error (RMSE) of 0.006
Angstroms which is half that of Vegards Law RMSE (0.012 Angstrom).
