Error: ksecul/zpotrf failed:   52   60   at K   14  0.083333

Error: ksecul/zpotrf failed:   60   60   at K    3  0.416667

Error: ksecul/zpotrf failed:   53   60   at K    4  0.416667

Error: ksecul/zpotrf failed:   52   60   at K    5  0.416667

Error: ksecul/zpotrf failed:   55   60   at K   18  0.083333

Signal Caught:           15

Error: ksecul/zpotrf failed:   60   60   at K    8  0.250000

Error: ksecul/zpotrf failed:   52   60   at K    9  0.250000

Error: ksecul/zpotrf failed:   52   60   at K   10  0.250000

Error: ksecul/zpotrf failed:   52   60   at K   11  0.250000

Error: ksecul/zpotrf failed:   52   60   at K   12  0.250000

When I try to add electrical field to the system ,there is alaws the above err.What's the matter ? ,and my input is as follows :

# Task parameters

Calculate                     optimize

Opt_energy_convergence        2.0000e-005

Opt_gradient_convergence      4.0000e-003 A

Opt_displacement_convergence  5.0000e-003 A

Opt_iterations                1000

Opt_max_displacement          0.3000 A

Lattice_optimization          on

Simple_geometry_opt

Symmetry                      off

Max_memory                    16000

# Electronic parameters

Spin_polarization             unrestricted

Charge                        0

Basis                         dnd

Pseudopotential               dspp

Functional                    pbe

Aux_density                   octupole

Integration_grid              medium

Occupation                    thermal 0.008

Cutoff_Global                 3.4000 angstrom

Scf_density_convergence       1.0000e-005

Scf_charge_mixing             0.2000

Scf_spin_mixing               0.5000

Scf_iterations                999

Scf_diis                      6 pulay

Electric_Field                                0    0   -0.08

# Kpoint definition file (intervals/offset):

Kpoints                       file     6 6 1 0.0000 0.0000 0.0000

1.kpoints

# Calculated properties