Dear Pwscf users,<br>
<br>
I performed gamma-point phonon calculation for my system only including
some light elements. Some negative frequencies appear
as following. The structure has been
optimized first and the nscf calculation was also
performed. Does the negative frequencies indicate the structural
instability? or how to eliminate these imaginary frequencies during my
following calculations?<br>
<br>
=========<br>
q = ( 0.000000000 0.000000000 0.000000000 )<br>
<br>
**************************************************************************<br>
omega( 1) = -3.014004 [THz] = -100.537026 [cm-1]<br>
omega( 2) = -1.833969 [THz] = -61.175042 [cm-1]<br>
omega( 3) = -1.568539 [THz] = -52.321189 [cm-1]<br>
omega( 4) = -1.362118 [THz] = -45.435661 [cm-1]<br>
omega( 5) = -0.979698 [THz] = -32.679419 [cm-1]<br>
omega( 6)
= 3.631786 [THz]
= 121.144148 [cm-1]<br>
omega( 7)
= 4.565661 [THz]
= 152.295057 [cm-1]<br>
omega( 8)
= 4.870748 [THz]
= 162.471753 [cm-1]<br>
omega( 9)
= 5.926574 [THz]
= 197.690558 [cm-1]<br>
omega(10)
= 6.692205 [THz]
= 223.229420 [cm-1]<br>
omega(11)
= 6.751437 [THz]
= 225.205202 [cm-1]<br>
omega(12)
= 7.152446 [THz]
= 238.581500 [cm-1]<br>
omega(13)
= 7.290775 [THz]
= 243.195689 [cm-1]<br>
omega(14)
= 7.583548 [THz]
= 252.961623 [cm-1]<br>
omega(15)
= 7.848509 [THz]
= 261.799816 [cm-1]<br>
omega(16)
= 8.216032 [THz]
= 274.059149 [cm-1]<br>
omega(17)
= 8.450907 [THz]
= 281.893782 [cm-1]<br>
omega(18)
= 8.617843 [THz]
= 287.462209 [cm-1]<br>
omega(19)
= 8.874576 [THz]
= 296.025963 [cm-1]<br>
omega(20)
= 9.106260 [THz]
= 303.754152 [cm-1]<br>
omega(21)
= 9.776634 [THz]
= 326.115571 [cm-1]<br>
omega(22)
= 9.846084 [THz]
= 328.432188 [cm-1]<br>
omega(23) = 10.441744 [THz] = 348.301414 [cm-1]<br>
omega(24) = 10.901272 [THz] = 363.629712 [cm-1]<br>
omega(25) = 11.120174 [THz] = 370.931537 [cm-1]<br>
omega(26) = 11.296950 [THz] = 376.828190 [cm-1]<br>
omega(27) = 11.744897 [THz] = 391.770187 [cm-1]<br>
omega(28) = 11.823415 [THz] = 394.389308 [cm-1]<br>
omega(29) = 12.284723 [THz] = 409.776965 [cm-1]<br>
omega(30) = 12.879001 [THz] = 429.600078 [cm-1]<br>
omega(31) = 13.104238 [THz] = 437.113223 [cm-1]<br>
omega(32) = 13.295358 [THz] = 443.488354 [cm-1]<br>
omega(33) = 13.386218 [THz] = 446.519146 [cm-1]<br>
omega(34) = 13.536055 [THz] = 451.517199 [cm-1]<br>
omega(35) = 13.571174 [THz] = 452.688634 [cm-1]<br>
omega(36) = 14.064683 [THz] = 469.150452 [cm-1]<br>
omega(37) = 14.556450 [THz] = 485.554120 [cm-1]<br>
omega(38) = 14.667300 [THz] = 489.251729 [cm-1]<br>
omega(39) = 15.110352 [THz] = 504.030430 [cm-1]<br>
omega(40) = 15.395285 [THz] = 513.534849 [cm-1]<br>
omega(41) = 16.043631 [THz] = 535.161476 [cm-1]<br>
omega(42) = 16.936124 [THz] = 564.932033 [cm-1]<br>
omega(43) = 18.733204 [THz] = 624.876561 [cm-1]<br>
omega(44) = 18.876424 [THz] = 629.653928 [cm-1]<br>
omega(45) = 19.992373 [THz] = 666.878205 [cm-1]<br>
omega(46) = 21.505666 [THz] = 717.356559 [cm-1]<br>
omega(47) = 21.617840 [THz] = 721.098322 [cm-1]<br>
omega(48) = 22.309307 [THz] = 744.163333 [cm-1]<br>
omega(49) = 23.662551 [THz] = 789.303000 [cm-1]<br>
omega(50) = 24.061062 [THz] = 802.595969 [cm-1]<br>
omega(51) = 24.064277 [THz] = 802.703198 [cm-1]<br>
omega(52) = 25.648159 [THz] = 855.536168 [cm-1]<br>
omega(53) = 26.862084 [THz] = 896.028637 [cm-1]<br>
omega(54) = 26.984089 [THz] = 900.098318 [cm-1]<br>
omega(55) = 28.413367 [THz] = 947.774196 [cm-1]<br>
omega(56) = 28.483349 [THz] = 950.108578 [cm-1]<br>
omega(57) = 28.903442 [THz] = 964.121470 [cm-1]<br>
omega(58) = 29.425892 [THz] = 981.548629 [cm-1]<br>
omega(59) = 29.797340 [THz] = 993.938893 [cm-1]<br>
omega(60) = 30.194172 [THz] = 1007.175875 [cm-1]<br>
omega(61) = 30.533468 [THz] = 1018.493632 [cm-1]<br>
omega(62) = 30.805908 [THz] = 1027.581303 [cm-1]<br>
omega(63) = 31.041973 [THz] = 1035.455634 [cm-1]<br>
omega(64) = 32.094778 [THz] = 1070.573675 [cm-1]<br>
omega(65) = 33.759643 [THz] = 1126.107965 [cm-1]<br>
omega(66) = 33.969486 [THz] = 1133.107616 [cm-1]<br>
omega(67) = 36.434092 [THz] = 1215.318565 [cm-1]<br>
omega(68) = 36.726631 [THz] = 1225.076683 [cm-1]<br>
omega(69) = 39.522021 [THz] = 1318.321478 [cm-1]<br>
omega(70) = 39.623203 [THz] = 1321.696562 [cm-1]<br>
omega(71) = 40.034020 [THz] = 1335.400026 [cm-1]<br>
omega(72) = 40.044563 [THz] = 1335.751729 [cm-1]<br>
omega(73) = 50.292137 [THz] = 1677.576257 [cm-1]<br>
omega(74) = 50.298606 [THz] = 1677.792065 [cm-1]<br>
omega(75) = 51.050051 [THz] = 1702.857719 [cm-1]<br>
omega(76) = 51.176742 [THz] = 1707.083716 [cm-1]<br>
omega(77) = 53.131701 [THz] = 1772.294552 [cm-1]<br>
omega(78) = 53.564853 [THz] = 1786.743033 [cm-1]<br>
omega(79) = 53.946325 [THz] = 1799.467683 [cm-1]<br>
omega(80) = 54.547644 [THz] = 1819.525644 [cm-1]<br>
omega(81) = 55.855114 [THz] = 1863.138433 [cm-1]<br>
omega(82) = 56.009839 [THz] = 1868.299538 [cm-1]<br>
omega(83) = 56.878920 [THz] = 1897.289172 [cm-1]<br>
omega(84) = 56.962499 [THz] = 1900.077075 [cm-1]<br>
omega(85) = 57.147227 [THz] = 1906.238980 [cm-1]<br>
omega(86) = 57.294672 [THz] = 1911.157244 [cm-1]<br>
omega(87) = 58.113524 [THz] = 1938.471399 [cm-1]<br>
omega(88) = 58.186280 [THz] = 1940.898280 [cm-1]<br>
omega(89) = 60.420046 [THz] = 2015.409202 [cm-1]<br>
omega(90) = 60.431210 [THz] = 2015.781574 [cm-1]<br>
**************************************************************************<br>
=========<br>
<br>
Regards,<br>
C.H.<br clear="all"><br>-- <br>============================<br>C.H. Hu<br>Postdoctoral fellow<br>Chimie et Physico-Chimie appliquees<br>Institut Francais du Petrole (IFP)<br>Rueil-Malmaison, France<br>E_mail: <a href="mailto:chaohao.mse@gmail.com">
chaohao.mse@gmail.com</a><br>============================