relaxation of fcc bulk lattice results in hcp coordinates

structure determination,...

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erichmond
Posts: 25
Joined: Fri Dec 23, 2016 12:00 am

relaxation of fcc bulk lattice results in hcp coordinates

Post by erichmond » Sun Jan 10, 2021 11:44 pm

I ran a relaxation file (input file attached ) in which I simultaneously tested five values of tsmear (0.0001., 0.0002, 0.0003, 0.0004, 0.0005) and 5 values of ngkpt (2 2 2, 4 4 4, 6 6 6, 8 8 8, 10 10 10). The input values of acell with ao = 3.8907 A were 2*2.75114 A 6.73889 A for the Pd(111) hexagonal face. angdeg = 90 90 120 and occopt = 2 and ionmov =2.

The output file was too large to attach gave tsmear = 0.0005 and ngkpt = 4 4 4 with a base vector ao/sqrt(2) = 2.72225 A and a interlayer distance ao/sqrt(3) = 2.37701 A. Back calculating, I find that for the base vector aob = 2.72225*sqrt(2) = 3.84986 A and for the interlayer vector aoi = 2.37701*sqrt(3) = 4.11710 A, such that c/a = 1.0694, when c/a should equal 1.

The relaxation coordinates, tsmear, ngkpt, were chosen with the lowest ground state energy.

My question is why c/a =/ 1? Did I do something wrong? Your input is desired!
Eliezer
Attachments
bulkPdkptopt021120.in
(2.69 KiB) Downloaded 8 times

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