原文地址:error termination-link 9999作者:每天进步一点点  ......i think yo r problem with link 9999 depends on the type of job yo r n. i m doing a lot of dft calc lations and very often the energy of of the geometry optmisations is not converging. on the contrary the force constants and the energy begin to oscillate. witho t a maxi m m of geometry optimisations s ch job co ld r n for a very long time witho t finding an end. if yo are also doing this kind of jobs (dft or hf calc lations) then have a look on yo r o tp t file. at the end of the last geometry sho ld be mentioned that the maxim m n mber of geometry optimisations is exceeded. the maxim m n mber of geom. calc lations is controlled by the keyword opt(maxcyc=n). to make the energy better converging it is very often helpf l to calc late the hesse matrix controlled by the keyword opt(calcfc) - only before the first geom. optmisation or by opt(calcall) - before every geom. optimization - or by iop(140=n) - every n steps, also possible when analytical calc lations of the hesse matrix are not possible. an other (and additional to the first s ggestions) possibility to make ga ssian better finding the minim m is to red ce the maxim m stepsize between the geometry optimisations controlled by iop(18=n) - opt(stepsize=n) is not working. i have made good experience with iop(18=10)....... sol tions from richmond: 1. 重新画结构; 2. 步长减小,#[theory][basis] iop(513=1) iop(211=1) iop(18=1) nosymm; 3. 在log.file中取energy和rms都比较低的结构,用这个结构继续算; 4. 如果log的str ct re正常,同时结算结果收敛,则认为计算结果合理.