First, you had better check the log file of your job. Particularly, see whether the total charge is converged to zero or not. If the total charge is converged to nearly zero, the 3rd and 4th parameters mentioned by you need to be tuned.
You are right. I first check my structure, then read my log file to check the charge. However, everything is OK, shown as follow.
# sc 45 : q = 277.45785 e Etot = -1292.40783 Ry dRho = 1.1254E-02 dEtot = -4.0064E-03 Ry
# sc 46 : q = 277.43865 e Etot = -1292.40513 Ry dRho = 7.4815E-03 dEtot = 2.6987E-03 Ry
# sc 47 : q = 277.43211 e Etot = -1292.40419 Ry dRho = 3.2435E-03 dEtot = 9.4009E-04 Ry
# sc 48 : q = 277.41565 e Etot = -1292.40180 Ry dRho = 6.6191E-03 dEtot = 2.3908E-03 Ry
# sc 49 : q = 277.45588 e Etot = -1292.40747 Ry dRho = 1.5931E-02 dEtot = -5.6712E-03 Ry
# sc 50 : q = 277.25674 e Etot = -1292.37649 Ry dRho = 8.4306E-02 dEtot = 3.0977E-02 Ry
# sc 51 : q = 277.35372 e Etot = -1292.39248 Ry dRho = 4.2263E-02 dEtot = -1.5981E-02 Ry
# sc 52 : q = 277.40286 e Etot = -1292.39985 Ry dRho = 2.0517E-02 dEtot = -7.3707E-03 Ry
# sc 53 : q = 277.43945 e Etot = -1292.40509 Ry dRho = 1.4680E-02 dEtot = -5.2436E-03 Ry
# sc 54 : q = 277.35574 e Etot = -1292.39272 Ry dRho = 3.4311E-02 dEtot = 1.2374E-02 Ry
# sc 55 : q = 277.35565 e Etot = -1292.39271 Ry dRho = 6.3075E-05 dEtot = 7.3768E-06 Ry
Zh, thanks, any other suggestion?