[Pw_forum] Initial geometry optimization cannot converge

[Chenyang Lee]

Dear experts in PWforum,

I am experiencing difficulties relaxing some of the structures of B-HAp. Because the Boron group substitutions are proposed (unknown), thus the initial structure may deviate a lot from the final optimized one. Quantum Espresso seems not to be very capable to do these jobs (no offense) and the SCF cycles usually exceed 500 steps and it still cannot converge. 
I am attaching the input file, and I’d appreciate it if someone who is able to identify the problem can help me solve it.

Thank you very much,
Chenyang
__
Chenyang Li
Undergraduate Student, Materials Science and Engineering
The Pennsylvania State University, University Park
Phone: (814)441-4312

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&control
    calculation = 'vc-relax'
    restart_mode = 'from_scratch'
    prefix = ‘BHAp'
    pseudo_dir = '/gpfs/home/col5422/work/HAp/pseudo/'
    outdir = './scratch/'
    tprnfor = .true.
    forc_conv_thr = 1e-4
    etot_conv_thr = 1e-6
    nstep = 500
/
&system
    ibrav = 14
    A = 9.4166
    B = 9.4166
    C = 6.8745
    cosAC = 0.0
    cosAB = -0.5
    cosBC = 0.0
    nat = 52
    ntyp = 6
    ecutwfc = 40
    ecutrho = 400
    nosym = .true.
    occupations = 'smearing'
    smearing = 'gaussian'
    degauss = 0.02
/
&electrons
    electron_maxstep = 500
    diagonalization = 'david'
    mixing_mode = 'plain'
    mixing_beta = 0.3
    conv_thr = 1e-6
/
&ions
    ion_dynamics = ‘damp'
/
&cell
    cell_dynamics = ‘damp-pr'
/

ATOMIC_SPECIES
H   1  H.pbe-kjpaw_psl.0.1.upf
B   1  B.pbe-n-kjpaw_psl.0.1.upf
C   1  C.pbe-n-kjpaw_psl.0.1.upf
O   1  O.pbe-n-kjpaw_psl.0.1.upf
P    1  P.pbe-n-kjpaw_psl.0.1.upf
Ca  1  Ca.pbe-spn-kjpaw_psl.0.2.3.upf

ATOMIC_POSITIONS crystal
H     0.000000   0.000000   0.400000
H     0.000000   0.000000   0.900000
H     0.567369   0.551274   0.972591
H     0.629383   0.851436   0.797858
H     0.357078   0.434312   0.660517
H     0.809237   0.663097   0.589841
B     0.581602   0.618142   0.689068
C     0.310984   0.129561   0.635342
O     0.348000   0.259000   0.073000
O     0.741000   0.089000   0.073000
O     0.911000   0.652000   0.073000
O     0.259000   0.911000   0.573000
O     0.089000   0.348000   0.573000
O     0.259000   0.911000   0.927000
O     0.089000   0.348000   0.927000
O     0.348000   0.259000   0.427000
O     0.741000   0.089000   0.427000
O     0.911000   0.652000   0.427000
O     0.329000   0.484000   0.250000
O     0.589000   0.466000   0.250000
O     0.516000  -0.155000   0.250000
O     0.534000   0.123000   0.250000
O     1.155000   0.671000   0.250000
O     0.877000   0.411000   0.250000
O     0.484000   1.155000   0.750000
O     0.466000   0.877000   0.750000
O    -0.155000   0.329000   0.750000
O     0.123000   0.589000   0.750000
O     0.000000   0.000000   0.250000
O     0.000000   0.000000   0.750000
O     0.603664   0.524999   0.843110
O     0.718661   0.681136   0.557507
O     0.546871   0.739153   0.774413
O     0.441199   0.509454   0.566674
O     0.464549   0.231819   0.634250
O     0.235429   0.067896   0.472588
O     0.237756   0.091652   0.804032
P     0.400000   0.369000   0.250000
P     0.631000   0.031000   0.250000
P     0.969000   0.600000   0.250000
P     0.369000   0.969000   0.750000
P     0.031000   0.400000   0.750000
Ca    0.333333   0.666667   0.001000
Ca    0.666667   0.333333   0.501000
Ca    0.666667   0.333333   0.999000
Ca    0.333333   0.666667   0.499000
Ca    0.246000   0.993000   0.250000
Ca    0.007000   0.253000   0.250000
Ca    0.747000   0.754000   0.250000
Ca    0.754000   0.007000   0.750000
Ca    0.993000   0.747000   0.750000
Ca    0.253000   0.246000   0.750000

K_POINTS automatic
4 4 4 1 1 1
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