Structural, electronic and magnetic properties of V(2)O(5-x): An ab initio study

Z R Xiao, G Y Guo
Journal of Chemical Physics 2009 June 7, 130 (21): 214704
Pure V(2)O(5) is a diamagnetic layered semiconductor with many applications such as catalysis. In this paper, we study oxygen vacancy-induced changes in the atomic and electronic structures as well as magnetic properties of V(2)O(5-x) within spin density functional theory with generalized gradient approximation. Both the supercell approach and virtual crystal approximation are used to simulate the oxygen-deficient V(2)O(5-x) with vacancy concentration x up to 0.5. The 1x2x2 supercell calculations with one O vacancy predict that the formation energies of the apical (O(1)), bridge (O(2)), and chain (O(3)) oxygen vacancies are, respectively, 2.48, 4.17, and 4.44 eV/vacancy, and hence that the O vacancies in V(2)O(5-x) would be predominantly of the O(1) type. The local structural distortions of the V atoms next to the O vacancies are found to be large for high vacancy density x(x>0.25), and for x approximately 0.5, even the crystal lattice changes from the orthorhombic to monoclinic symmetry. In all the cases considered, an O vacancy-induced stable or metastable ferromagnetic state with spin magnetic moment of approximately 2.0mu(B)/vacancy is found. For x below approximately 0.13 and 0.19<x< approximately 0.45, the ferromagnetic state would be the ground state, while for 0.45<or=x<or=0.5, the antiferromagnetic state with the V spins on neighboring rungs (AF-2) being antiparallel is the ground state. Importantly, this suggests that undoped V(2)O(5-x) with x<or=0.13 and 0.19<x< approximately 0.45 would be a diluted ferromagnetic semiconductor. The AF-2, however, disappears for x<or=0.25, while the antiferromagnetic state with the V spins on neighboring ladders being antiparallel (AF-1) occurs for the entire range of x studied. Nevertheless, the AF-1 is energetically more favorable than the ferromagnetic state only in 0.13<x< approximately 0.19. For low O vacancy concentrations (x<0.25), the electronic structure of V(2)O(5-x) is very similar to that of the perfect bulk V(2)O(5), except that 2x electrons now occupy the low V d(xy) dominant conduction bands which are exchange split. Majority of the magnetization is located on the d(xy)-orbitals of the V atoms near the O vacancy site. For larger x values, however, the electronic structure may change significantly, and, in particular, the V d-orbital character of the low conduction bands can be altered completely. Analysis of the calculated electronic structure reveals that the oxygen vacancy-induced magnetization in V(2)O(5-x) results primarily from the Stoner mechanism.

Full Text Links

Find Full Text Links for this Article


You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read

Save your favorite articles in one place with a free QxMD account.


Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"