A theoretical study of the structural phases of Group 5B - 6B metals and their transport properties

TL;DR

This study uses computational methods to predict stable and metastable phases of Group 5B-6B bcc metals and examines how their structure influences electrical transport properties, revealing differences in conductivity between phases.

Contribution

It provides a detailed theoretical analysis of phase stability and transport properties of Group 5B-6B metals, including the prediction of metastable phases and their electrical behavior.

Findings

Metastable bct phases are predicted for all studied metals.

Bct phases of Group 5B metals are more conductive than bcc phases.

Bct phases of Group 6B metals are less conductive than bcc phases.

Abstract

In order to predict the stable and metastable phases of the bcc metals in the block of the Periodic Table defined by groups 5B to 6B and periods 4 to 6, as well as the structure dependence of their transport properties, we have performed full potential computations of the total energies per unit cell as a function of the c/a ratio at constant experimental volume. In all cases, a metastable body centered tetragonal (bct) phase was predicted from the calculations. The total energy differences between the calculated stable and metastable phases ranged from 0.09 eV/cell (vanadium) to 0.39 eV/cell (tungsten). The trends in resistivity as a function of structure and atomic number are discussed in terms of a model of electron transport in metals. Theoretical calculations of the electrical resistivity and other transport properties show that bct phases derived from group 5B elements are more conductive than the corresponding bcc phases, while bct phases formed from group 6B elements are less conductive than the corresponding bcc phases. Special attention is paid to the phases of tantalum where we show that the frequently observed beta phase is not a simple tetragonal distortion of bcc tantalum.