Comment on ``Sodium Pyroxene NaTiSi${}_2$O${}_6$: Possible Haldane Spin-1 Chain System''

Abstract

Magnetic and electronic properties of NaTiSi${}_2$O${}_6$ in low temperature phase were studied in the framework of the LDA+U approximation. We stress that neglecting correlation effects in LSDA calculations one obtains not only several times smaller value of the band gap, but also fails to describe magnetic properties of NaTiSi${}_2$O${}_6$. Our LDA+U results confirm formation of singlet Ti-Ti dimers in low temperature phase of NaTiSi${}_2$O${}_6$ driven by corresponding orbital ordering [J. Phys. Soc. Jpn. 71, 1423 (2002)], but strongly disagree with the LSDA results and interpretations of Phys. Rev. Lett. 93, 036401 (2004).

1 table. Submitted to Phys. Rev. Lett. as a Comment