Lattice constant of rutile

Posted on : December 07, 2017 (Thu) 08:58:30

by Hiroyuki Fujita

Dear Professors,

I try to calculate the electronic structure of rutile (TiO2) using the following input file:

c----------------------TiO2----------------------------------
go dat/tio2
c------------------------------------------------------------
c brvtyp a c/a b/a alpha beta gamma
st latc , 0.6440 , , , , ,
c------------------------------------------------------------
c edelt ewidth reltyp sdftyp magtyp record
0.001 4 sra vwn mag 2nd
c------------------------------------------------------------
c outtyp bzqlty maxitr pmix
update h 600 0.006
c------------------------------------------------------------
c ntyp
2
c------------------------------------------------------------
c type ncmp rmt field mxl anclr conc
Ti 1 0 0.0 2 22 100
O 1 0 0.0 2 8 100
c------------------------------------------------------------
c natm
6
c------------------------------------------------------------
c atmicx atmtyp
0a 0b 0c Ti
0.5a 0.5b 0.5c 　　 Ti
0.305a 0.305b 0c O
0.695a 0.695b 　0c 　O
0.805a 0.195b 0.5c O
0.195a 0.805b 0.5c O



c------------------------------------------------------------


Here the parameter 'latc' is varied to find the optimal lattice constant. Other parameters are fixed to those on the Aflow website

http://aflowlib.org/CrystalDatabase/A2B_tP6_136_f_a.html


According to the Aflow (and other literatures) the lattice constant should be around 8.68 in Bohr radius. However, the result is as follows. The energy constantly decrease as we increase the lattice constant.

8.4000 -4005.3252607 -0.00000
8.5000 -4005.4380139 0.00000
8.6000 -4005.5345271 0.00000
8.7000 -4005.6164009 0.00000
8.8000 -4005.6910509 -0.00000
8.9000 -4005.7418053 -0.00000
9.0000 -4005.7876008 0.00000
9.1000 -4005.8235751 -0.00000
9.2000 -4005.8506650 0.00000
9.3000 -4005.8697262 0.00000
9.4000 -4005.8815720 0.00000
9.5000 -4005.8867209 0.00000

How can I fix this?

Thank you for your support in advance.

Hiroyuki FUJITA